cp's OEIS Frontend

A339910 After 1, numbers k > 1 such that k has fewer prime divisors than k-1, when they are counted with multiplicity.

%I A339910 #18 May 15 2023 08:44:27
%S A339910 1,5,7,9,11,13,17,19,21,23,25,29,31,33,37,41,43,46,47,49,51,53,55,57,
%T A339910 59,61,65,67,69,71,73,77,79,81,82,83,85,89,91,93,97,101,103,105,106,
%U A339910 107,109,111,113,115,118,121,127,129,131,133,137,139,141,145,149,151,153,155,157,161,163,166,167,169,173,177,179
%N A339910 After 1, numbers k > 1 such that k has fewer prime divisors than k-1, when they are counted with multiplicity.
%C A339910 List of starts of nondecreasing runs of values of A001222 (= bigomega, number of prime factors, when counted with multiplicity).
%C A339910 Differs from A303578 (a similar sequence computed for tau, the number of divisors) for the first time at n=44, where a(44) = 105, a term missing from A303578.
%H A339910 Antti Karttunen, <a href="/A339910/b339910.txt">Table of n, a(n) for n = 1..28208; all terms <= 65537</a>
%t A339910 1 + {0}~Join~Position[Sign@ Differences[Array[PrimeOmega, 180]], -1][[All, 1]] (* _Michael De Vlieger_, Dec 22 2020 *)
%o A339910 (PARI) isA339910(n) = ((1==n)||(bigomega(n)<bigomega(n-1)));
%Y A339910 Cf. A001222.
%Y A339910 One more than A322839.
%Y A339910 Cf. A339911, A339912 for subsequences.
%Y A339910 Cf. also A303578.
%K A339910 nonn
%O A339910 1,2
%A A339910 _Antti Karttunen_, Dec 22 2020