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 A157024 #15 Feb 27 2022 05:46:12
%S A157024 1,12,105,360,858,1680,2907,4620,6900,9828,13485,17952,23310,29640,
%T A157024 37023,45540,55272,66300,78705,92568,107970,124992,143715,164220,
%U A157024 186588,210900,237237,265680,296310,329208,364455,402132,442320,485100,530553,578760,629802
%N A157024 a(0)=1, a(n) = (3n-1)*3n*(3n+1)/2 for n>0.
%F A157024 Sum_{n>=0} 1/a(n) = log(3).
%F A157024 G.f.: (1+8x+63x^2+8x^3+x^4)/(1-x)^4.
%F A157024 a(n) = A027480(3n-1), n>0. - _R. J. Mathar_, Apr 07 2009
%F A157024 Sum_{n>=0} (-1)^n/a(n) = 4*log(2)/3. - _Amiram Eldar_, Feb 27 2022
%t A157024 nxt[{n_,a_}]:={n+1,((3n)(3n-1)(3n+1))/2}; NestList[nxt,{0,1},40][[All,2]]/.(0->Nothing) (* _Harvey P. Dale_, Sep 24 2016 *)
%Y A157024 Cf. A002391, A027480, A058962, A097321, A154920.
%K A157024 nonn
%O A157024 0,2
%A A157024 _Jaume Oliver Lafont_, Feb 21 2009