1,1

Characteristic function of A014613.

See A101638 for the inverse Moebius transform of this sequence.

Antti Karttunen, Table of n, a(n) for n = 1..65537

Eric Weisstein's World of Mathematics, Almost Prime.

Index entries for characteristic functions

Index entries for sequences computed from exponents in factorization of n

a(100) = 1 because 100 = 2 * 2 * 5 * 5 is the product of exactly 4 primes and thus is a 4-almost prime.

(PARI) a(n)=bigomega(n)==4 \\ Charles R Greathouse IV, Jan 31 2017

Cf. A101638, A014613, A000040, A001358, A014612, A014614.

Sequence in context: A277164 A011730 A295884 * A337380 A011729 A297044

Adjacent sequences: A101634 A101635 A101636 * A101638 A101639 A101640

easy,nonn

Jonathan Vos Post, Dec 10 2004

Name edited by Antti Karttunen, Oct 08 2017

approved