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 A361273 #8 Mar 09 2023 20:02:37 %S A361273 1,1,1,3,6,13,20,37,47,81,91,151,156,253,246,393,365,577,517,811,706, %T A361273 1101,936,1453,1211,1873,1535,2367,1912,2941,2346,3601,2841,4353,3401, %U A361273 5203,4030,6157,4732,7221,5511,8401,6371,9703,7316,11133,8350,12697,9477,14401,10701 %N A361273 Number of 1324-avoiding even Grassmannian permutations of size n. %C A361273 A permutation is said to be Grassmannian if it has at most one descent. A permutation is even if it has an even number of inversions. %H A361273 Juan B. Gil and Jessica A. Tomasko, <a href="https://arxiv.org/abs/2207.12617">Pattern-avoiding even and odd Grassmannian permutations</a>, arXiv:2207.12617 [math.CO], 2022. %H A361273 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-6,0,4,0,-1). %F A361273 G.f.: -(x^7+2*x^6-7*x^5-8*x^4+x^3+3*x^2-x-1)/((x+1)^4*(x-1)^4). %e A361273 For n=4 the a(4) = 6 permutations are 1234, 1342, 1423, 2314, 3124, 3412. %Y A361273 Cf. A356185, A361270, A361272. %K A361273 nonn,easy %O A361273 0,4 %A A361273 _Juan B. Gil_, Mar 09 2023