Search: a134361 -id:a134361
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A130916
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a(n) = smallest integer >= n which has only prime factors 2, 3 and 5.
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+10
4
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1, 2, 3, 4, 5, 6, 8, 8, 9, 10, 12, 12, 15, 15, 15, 16, 18, 18, 20, 20, 24, 24, 24, 24, 25, 27, 27, 30, 30, 30, 32, 32, 36, 36, 36, 36, 40, 40, 40, 40, 45, 45, 45, 45, 45, 48, 48, 48, 50, 50, 54, 54, 54, 54, 60, 60, 60, 60, 60, 60, 64, 64, 64, 64, 72, 72, 72, 72, 72
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OFFSET
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1,2
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COMMENTS
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This group of sequences is useful when looking for a number >= n to use as the basis for a Fast Fourier Transform when you have n data points.
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LINKS
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MATHEMATICA
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si[n_]:=Module[{k=n}, While[Max[FactorInteger[k][[All, 1]]]>5, k++]; k]; Array[ si, 70] (* Harvey P. Dale, Oct 14 2019 *)
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PROG
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(R) f <- function(n) nextn(n, factors = c(2, 3, 5))
a <- matrix(1:256, ncol=1)
apply(a, 1, f)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A151969
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a(n) = smallest integer >= n which has only prime factors 2 and 5.
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+10
4
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1, 2, 4, 4, 5, 8, 8, 8, 10, 10, 16, 16, 16, 16, 16, 16, 20, 20, 20, 20, 25, 25, 25, 25, 25, 32, 32, 32, 32, 32, 32, 32, 40, 40, 40, 40, 40, 40, 40, 40, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 80, 80, 80, 80, 80
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Module[{upto=100, pwr, f25}, pwr=Ceiling[Log[2, upto]]; f25=Select[ Sort[ Flatten[ Table[Times@@@Union[Sort/@Tuples[{2, 5}, n]], {n, 0, pwr}]]], #<= upto&]; Table[SelectFirst[f25, #>i&], {i, 0, upto-1}]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, Jan 28 2016 *)
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PROG
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(R) f <- function(n) nextn(n, factors = c(2, 5))
a <- matrix(1:256, ncol=1)
apply(a, 1, f)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A151970
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a(n) = smallest integer >= n which has only prime factors 3 and 5.
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+10
2
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1, 3, 3, 5, 5, 9, 9, 9, 9, 15, 15, 15, 15, 15, 15, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 27, 27, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75, 75
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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PROG
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(R) f <- function(n) nextn(n, factors = c(3, 5))
a <- matrix(1:256, ncol=1)
apply(a, 1, f)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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