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 A117948 #23 Dec 15 2024 05:18:42
%S A117948 1,6,28,36,48,72,144,168,182,180,372,576,280,336,864,720,558,702,1120,
%T A117948 1080,1024,1008,1296,2016,1178,1344,3600,2016,1320,2160,2304,3720,
%U A117948 2736,1836,4704,4212,2736,2280,5040,6048,2604,4992,5588,4752,5304,3312
%N A117948 Sum of the divisors of pentagonal numbers.
%H A117948 Amiram Eldar, <a href="/A117948/b117948.txt">Table of n, a(n) for n = 1..10000</a>
%F A117948 a(n) = sigma(n(3n-1)/2), where sigma is the sum of divisors function. - _Emeric Deutsch_, Apr 15 2006
%F A117948 Sum_{k=1..n} a(k) ~ (9/10) * n^3. - _Amiram Eldar_, Dec 14 2024
%e A117948 a(5) = 48 because the divisors of 5*(3*5-1)/2 = 35 are 1, 5, 7 and 35, having sum 48.
%p A117948 with(numtheory): seq(sigma(n*(3*n-1)/2),n=1..46); # _Emeric Deutsch_, Apr 15 2006
%t A117948 Table[DivisorSigma[1,(n(3n-1))/2],{n,50}] (* _Harvey P. Dale_, Jul 05 2015 *)
%o A117948 (PARI) a(n) = sigma(n*(3*n-1)/2); \\ _Amiram Eldar_, Dec 14 2024
%Y A117948 Cf. A000203, A000326, A074285, A117949.
%K A117948 easy,nonn
%O A117948 1,2
%A A117948 _Jonathan Vos Post_, Apr 04 2006
%E A117948 a(0) removed by _Amiram Eldar_, Aug 17 2019