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A200925
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Numbers n such that Omega(n) = Omega(n - Omega(n)), where Omega = A001222.
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2
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1, 3, 6, 30, 35, 40, 45, 51, 57, 60, 66, 78, 87, 88, 93, 95, 102, 104, 105, 117, 121, 123, 136, 140, 143, 145, 156, 161, 174, 175, 185, 187, 203, 205, 215, 217, 219, 221, 232, 237, 245, 249, 258, 261, 267, 282, 285, 289, 291, 301, 303, 305, 321, 323, 325, 329
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Omega=A001222: Number of prime divisors counted with multiplicity.
A198327 is a subsequence because, if n and n-2 are semiprimes, Omega(n) = 2, and n - 2 is semiprime, therefore Omega(n-2) = 2.
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LINKS
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EXAMPLE
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a(5) = 35 because Omega(35) = 2 and Omega(35 - 2) = Omega(33) = 2.
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MAPLE
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with(numtheory):
isA200925 := proc(n)
bigomega(n-bigomega(n)) = bigomega(n) ;
end proc:
for n from 1 to 400 do
if isA200925(n) then printf("%d, ", n) ; end if;
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MATHEMATICA
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Select[Range[329], PrimeOmega[#] == PrimeOmega[# - PrimeOmega[#]] &] (* T. D. Noe, Nov 29 2011 *)
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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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