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 A137357 #17 Mar 17 2024 15:10:30
%S A137357 0,1,2,3,4,5,7,12,23,44,80,138,230,379,629,1060,1810,3109,5336,9120,
%T A137357 15521,26349,44713,75949,129177,219918,374521,637699,1085401,1846804,
%U A137357 3141826,5344988,9093989,15474230,26332515,44810670,76253683,129755543,220790480
%N A137357 a(n) = Sum_{k <= n/2 } binomial(n-2k, 3k+1).
%D A137357 D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.4.
%H A137357 Paolo Xausa, <a href="/A137357/b137357.txt">Table of n, a(n) for n = 0..1000</a>
%H A137357 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,1).
%F A137357 G.f.: x*(x-1) / (x^5+x^3-3*x^2+3*x-1). - _Colin Barker_, Jan 23 2013
%t A137357 LinearRecurrence[{3, -3, 1, 0, 1}, Range[0, 4], 50] (* _Paolo Xausa_, Mar 17 2024 *)
%Y A137357 Cf. A137356, A137358, A137359, A137360, A137361, A136444.
%K A137357 nonn,easy
%O A137357 0,3
%A A137357 _Don Knuth_, Apr 11 2008