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 A137358 #14 Mar 17 2024 12:54:43
%S A137358 0,0,1,3,6,10,15,22,34,57,101,181,319,549,928,1557,2617,4427,7536,
%T A137358 12872,21992,37513,63862,108575,184524,313701,533619,908140,1545839,
%U A137358 2631240,4478044,7619870,12964858,22058847,37533077,63865592,108676262,184929945,314685488
%N A137358 a(n) = Sum_{k <= n/2 } binomial(n-2k, 3k+2).
%D A137358 D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.4.
%H A137358 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,1).
%F A137358 a(0)=0, a(1)=0, a(2)=1, a(3)=3, a(4)=6, a(n)=3*a(n-1)-3*a(n-2)+ a(n-3)+ a(n-5). - _Harvey P. Dale_, Nov 06 2012
%F A137358 G.f.: -x^2/(x^5+x^3-3*x^2+3*x-1). - _Colin Barker_, Jan 23 2013
%t A137358 Table[Sum[Binomial[n-2k,3k+2],{k,0,Floor[n/2]}],{n,0,50}] (* or *) LinearRecurrence[{3,-3,1,0,1},{0,0,1,3,6},50] (* _Harvey P. Dale_, Nov 06 2012 *)
%Y A137358 Cf. A137356, A137357, A137359, A137360, A137361, A136444.
%K A137358 nonn,easy
%O A137358 0,4
%A A137358 _Don Knuth_, Apr 11 2008