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 A130656 #19 Mar 15 2024 05:52:18
%S A130656 1,4,18,32,75,108,196,256,405,500,726,864,1183,1372,1800,2048,2601,
%T A130656 2916,3610,4000,4851,5324,6348,6912,8125,8788,10206,10976,12615,13500,
%U A130656 15376,16384,18513,19652,22050,23328,26011,27436,30420,32000,35301,37044
%N A130656 Interlacing n^3/2 and n^2(n + 1)/2.
%H A130656 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,3,-3,-3,3,1,-1).
%F A130656 a(n) = n^2 * floor((n + 1)/2).
%F A130656 G.f.: x*(1+3*x+11*x^2+5*x^3+4*x^4)/((1-x)^4*(1+x)^3). - _R. J. Mathar_, Sep 09 2008
%F A130656 a(n) = a(n-1)+ 3*a(n-2)-3*a(n-3)-3*a(n-4)+3*a(n-5)+a(n-6)-a(n-7), a(1)=1, a(2)=4, a(3)=18, a(4)=32, a(5)=75, a(6)=108, a(7)=196. - _Harvey P. Dale_, Feb 18 2015
%F A130656 Sum_{n>=1} 1/a(n) = zeta(3)/4 + Pi^2/4 - 2*log(2). - _Amiram Eldar_, Mar 15 2024
%p A130656 A130656:=n->n^2 * floor((n + 1)/2): seq(A130656(n), n=1..100); # _Wesley Ivan Hurt_, Jan 21 2017
%t A130656 a[n_Integer] := n^2 * Floor[(n + 1)/2]
%t A130656 LinearRecurrence[{1,3,-3,-3,3,1,-1},{1,4,18,32,75,108,196},50] (* _Harvey P. Dale_, Feb 18 2015 *)
%Y A130656 Cf. A093005 (quadratic equivalent), A065423 (linear equivalent).
%K A130656 easy,nonn
%O A130656 1,2
%A A130656 _Olivier Gérard_, Jun 21 2007