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 A377959 #8 Nov 12 2024 11:37:54
%S A377959 1,3,9,31,141,831,5773,45459,403161,3990331,43544721,518940423,
%T A377959 6706062949,93404895351,1394851282581,22230473112571,376610264357553,
%U A377959 6758060929028979,128047472471583001,2554547113522500591,53523844242070603581,1175091669834676927663
%N A377959 Expansion of e.g.f. exp(x - x^2)/(1 - x)^2.
%F A377959 a(n) = n! * Sum_{k=0..n} binomial(n-2*k+1,n-k) / k!.
%F A377959 a(n) = (n+2)*a(n-1) - 3*(n-1)*a(n-2) + 2*(n-1)*(n-2)*a(n-3) for n > 2.
%o A377959 (PARI) a(n) = n!*sum(k=0, n, binomial(n-2*k+1, n-k)/k!);
%Y A377959 Cf. A293604, A377958, A377960.
%Y A377959 Cf. A377954.
%K A377959 nonn
%O A377959 0,2
%A A377959 _Seiichi Manyama_, Nov 12 2024