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 A302181 #27 Nov 22 2024 15:49:29
%S A302181 1,5,62,1065,21714,492366,12004740,308559537,8255788970,227976044010,
%T A302181 6457854821340,186814834574550,5500292590186380,164387681345290500,
%U A302181 4976887208815547640,152378485941172462785,4711642301137121933850,146964278352052950118770,4619875954522866283392300
%N A302181 Number of 3D walks of type abb.
%C A302181 See Dershowitz (2017) for precise definition.
%H A302181 Nachum Dershowitz, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL20/Dershowitz/dersh3.html">Touchard's Drunkard</a>, Journal of Integer Sequences, Vol. 20 (2017), #17.1.5.
%F A302181 a(n) = Sum_{k=0..2*n} binomial(2*n, k) * A005558(k) * A126869(2*n-k). - _Mélika Tebni_, Nov 06 2024
%p A302181 C := n-> binomial(2*n, n)/(n+1): # Catalan numbers
%p A302181 A302181 := n-> add(binomial(2*n, k)*C(iquo(k+1, 2))*C(iquo(k, 2))*(2*iquo(k, 2)+1)*add((-1)^(k+j)*binomial(2*n-k, iquo(j,2)), j=0..2*n-k), k=0..2*n): seq(A302181(n), n = 0 .. 18); # _Mélika Tebni_, Nov 06 2024
%Y A302181 Cf. A000108, A000984, A002212, A002896, A005572, A026375, A064037, A081671, A138547, A145847, A145867, A150500, A202814.
%Y A302181 Cf. A005558, A126869.
%K A302181 nonn,walk
%O A302181 0,2
%A A302181 _N. J. A. Sloane_, Apr 09 2018
%E A302181 a(8)-a(18) from _Nachum Dershowitz_, Aug 03 2020