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 A350498 #33 Aug 17 2022 07:10:44
%S A350498 0,1,7,31,114,385,1250,3987,12619,39810,125425,394955,1243433,3914383,
%T A350498 12322293,38789576,122105944,384377494,1209981891,3808901216,
%U A350498 11990036895,37743426054,118812495000,374009739009,1177344897390,3706162867858,11666626518622,36725362368682,115607732787126,363921470561515
%N A350498 Convolution of triangular numbers with every third number of Narayana's Cows sequence.
%C A350498 This is the convolution of N(3*n-1) with t(n); in other words, a(n) = Sum_{i=1..n} N(3*i-1)*t(n-i) where N(k)=A000930(k) is the k-th number in Narayana's Cows sequence and t(k)=A000217(k) is the k-th triangular number.
%D A350498 G. Dresden and M. Tulskikh, "Convolutions of Sequences with Single-Term Signature Differences", preprint.
%H A350498 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (7,-18,23,-16,6,-1).
%F A350498 a(n) = N(3*n-1) - A000217(n) where N(k)=A000930(k).
%F A350498 G.f.: x^2/((1 - x)^3 * (1 - 4*x + 3*x^2 - x^3)).
%F A350498 a(n) = A052529(n)-A000217(n), n>0. - _R. J. Mathar_, Aug 17 2022
%e A350498 For n=4, a(4) = N(2)*t(3) + N(5)*t(2) + N(8)*t(1) + N(11)*t(0) = 1*6 + 4*3 + 13*1 + 41*0 = 31, where N(k)=A000930(k) and t(k)=A000217(k).
%t A350498 CoefficientList[
%t A350498 Series[x/((-1 + x)^3 (-1 + 4 x - 3 x^2 + x^3)), {x, 0, 30}], x]
%Y A350498 Cf. A000217, A000930.
%K A350498 nonn,easy
%O A350498 1,3
%A A350498 _Greg Dresden_, Jan 04 2022