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 A279290 #34 Jan 11 2025 03:12:05
%S A279290 1,1,1,65,1,217,1,577,730,1001,1,2009,1,2745,3376,4673,1,6778,1,9065,
%T A279290 9262,10649,1,16345,15626,17577,20413,24761,1,31592,1,37441,35938,
%U A279290 39305,42876,55226,1,54873,59320,73577,1,86310,1,95897,95230,97337,1,131033,117650,141626,132652,158249,1,183925,166376
%N A279290 Sum of cubes of nonprime divisors of n.
%H A279290 Harvey P. Dale, <a href="/A279290/b279290.txt">Table of n, a(n) for n = 1..1000</a>
%H A279290 <a href="/index/Su#sums_of_divisors">Index entries for sequences related to sums of divisors</a>.
%F A279290 a(n) = A001158(n) - A005064(n).
%F A279290 a(n) = 1 when n = 1 or n is prime.
%F A279290 a(p^k) = (p^(3*k+3) - 1)/(p^3 - 1) - p^3 when p is prime.
%e A279290 a(4) = 65 because 4 has 2 nonprime divisors {1,4} and 1^3 + 4^3 = 65.
%t A279290 Table[DivisorSum[n, #1^3 & , !PrimeQ[#1] & ], {n, 55}]
%t A279290 Table[DivisorSigma[3, n] - DivisorSum[n, #1^3 & , PrimeQ[#1] & ], {n, 55}]
%t A279290 Table[Total[Select[Divisors[n],!PrimeQ[#]&]^3],{n,60}] (* _Harvey P. Dale_, Aug 02 2024 *)
%o A279290 (PARI) a(n) = {my(f = factor(n)); sigma(f, 3) - sum(i=1, #f~, f[i, 1]^3);} \\ _Amiram Eldar_, Jan 11 2025
%Y A279290 Cf. A001158, A005064, A023890, A189120.
%K A279290 nonn,easy
%O A279290 1,4
%A A279290 _Ilya Gutkovskiy_, Dec 12 2016