OFFSET
1,2
COMMENTS
In A050150 but not here: [729, 15625, 59049, 117649, 531441]; here but not in A050150: [1, 6561, 390625]. - Klaus Brockhaus, Nov 01 2001
If "a(1) = 1," is removed from the definition, the subsequent terms remain the same, since 1 is the empty product. The resulting sequence then comprises the odd terms of A050376. - Peter Munn, Nov 03 2020
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
FORMULA
1 together with numbers of the form p^(2^k) where p is an odd prime and k is a nonnegative integer. [Corrected by Peter Munn, Nov 03 2020]
For n >= 2, a(n) = A336882(2^(n-2)). - Peter Munn, Nov 03 2020
EXAMPLE
After 13 the next term is 17 (not 15) as 15 = 3*5 divides the product of all the previous terms.
MATHEMATICA
a = {1}; Do[b = Apply[ Times, a]; k = 1; While[ IntegerQ[b/k], k += 2]; a = Append[a, k], { n, 2, 60} ]; a
nxt[{p_, on_}]:=Module[{c=on+2}, While[Divisible[p, c], c+=2]; {p*c, c}]; NestList[ nxt, {1, 1}, 60][[All, 2]] (* Harvey P. Dale, Jul 29 2021 *)
PROG
(Haskell)
a062090 n = a062090_list !! (n-1)
a062090_list = f [1, 3 ..] [] where
f (x:xs) ys = g x ys where
g _ [] = x : f xs (x : ys)
g 1 _ = f xs ys
g z (v:vs) = g (z `div` gcd z v) vs
-- Reinhard Zumkeller, Aug 16 2013
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
Amarnath Murthy, Jun 16 2001
EXTENSIONS
Corrected and extended by Dean Hickerson, Jul 10 2001
STATUS
approved