%I #23 May 21 2021 11:25:52

%S 1,1,1,1,3,1,1,1,3,1,3,1,3,3,1,1,3,1,3,3,3,1,3,1,3,1,3,1,4,1,1,3,3,3,

%T 3,1,3,3,3,1,4,1,3,3,3,1,3,1,3,3,3,1,3,3,3,3,3,1,4,1,3,3,1,3,4,1,3,3,

%U 4,1,3,1,3,3,3,3,4,1,3,1,3,1,4,3,3,3

%N a(n) = sigma(omega(n)).

%C If n is the product of k distinct primes, then a(n) = sigma(k).

%C Records occur at n = 2, 6, 30, 210, 30030, ... . - _R. J. Mathar_, Jun 18 2014

%C If n = p^k where p is prime and k is a positive integer, a(p^k) = sigma(omega(p^k)) = sigma(1) = 1. - _Wesley Ivan Hurt_, May 21 2021

%H G. C. Greubel, <a href="/A243915/b243915.txt">Table of n, a(n) for n = 2..5000</a>

%F a(n) = sigma(omega(n)) = A000203(A001221(n)).

%p with(numtheory):

%p A243915 := proc(n)

%p sigma(nops(factorset(n))) ;

%p end proc:

%p seq(A243915(n), n=2..100); # _R. J. Mathar_, Jun 18 2014

%t Table[DivisorSigma[1, PrimeNu[n]], {n, 2, 100}]

%o (PARI) for(n=2,50, print1(sigma(omega(n)), ", ")) \\ _G. C. Greubel_, May 17 2017

%Y Cf. A000203, A001221.

%K nonn,easy

%O 2,5

%A _Wesley Ivan Hurt_, Jun 14 2014