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 A046996 #19 Jan 04 2024 08:57:07
%S A046996 1,3,11,46,211,1037,5377,29101,163120,941480,5570280,33664996,
%T A046996 207249719,1296670793,8229378293,52895993341,343891293422,
%U A046996 2258771535962,14974619271658,100117092310368,674548712552456,4577138309318008,31261253291922136,214800030086785976
%N A046996 Number of Baxter permutations: A001181/2.
%H A046996 Alois P. Heinz, <a href="/A046996/b046996.txt">Table of n, a(n) for n = 2..1120</a>
%F A046996 a(n) = (1/2)*B(n, 1) where B(n, x) are the Baxter polynomials with coefficients A359363. - _Peter Luschny_, Jan 04 2024
%p A046996 a:= proc(n) option remember; `if`(n<4, 2*n-3,
%p A046996 ((7*n^2+7*n-2)*a(n-1)+8*(n-1)*(n-2)*a(n-2))/((n+2)*(n+3)))
%p A046996 end:
%p A046996 seq(a(n), n=2..25); # _Alois P. Heinz_, Jul 29 2022
%t A046996 Sum[Binomial[n+1, k-1] Binomial[n+1, k] Binomial[n+1, k+1], {k, 1, n}]/(2 Binomial[n+1, 1] Binomial[n+1, 2])
%o A046996 (SageMath)
%o A046996 def A046996(n): return PolyA359363(n, 1) // 2
%o A046996 print([A046996(n) for n in range(2, 26)]) # _Peter Luschny_, Jan 04 2024
%Y A046996 Cf. A359363.
%K A046996 nonn,easy
%O A046996 2,2
%A A046996 _N. J. A. Sloane_
%E A046996 More terms from _Olivier Gérard_, Jun 26 2001