This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A243915 #29 Apr 01 2025 19:52:19
%S A243915 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 A243915 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 A243915 4,1,3,1,3,3,3,3,4,1,3,1,3,1,4,3,3,3
%N A243915 a(n) = sigma(omega(n)).
%C A243915 If n is the product of k distinct primes, then a(n) = sigma(k).
%C A243915 Records occur at n = 2, 6, 30, 210, 30030, ... . - _R. J. Mathar_, Jun 18 2014 [The position of the n-th record is A002110(A002093(n)). - _Amiram Eldar_, Dec 29 2024]
%C A243915 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 A243915 G. C. Greubel, <a href="/A243915/b243915.txt">Table of n, a(n) for n = 2..5000</a>
%F A243915 a(n) = A000203(A001221(n)).
%p A243915 with(numtheory):
%p A243915 A243915 := proc(n)
%p A243915 sigma(nops(factorset(n))) ;
%p A243915 end proc:
%p A243915 seq(A243915(n), n=2..100); # _R. J. Mathar_, Jun 18 2014
%t A243915 Table[DivisorSigma[1, PrimeNu[n]], {n, 2, 100}]
%o A243915 (PARI) for(n=2,50, print1(sigma(omega(n)), ", ")) \\ _G. C. Greubel_, May 17 2017
%Y A243915 Cf. A000203 (sigma), A001221 (omega), A002110, A002093.
%K A243915 nonn,easy
%O A243915 2,5
%A A243915 _Wesley Ivan Hurt_, Jun 14 2014