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 A223659 #37 Feb 11 2024 23:45:33 %S A223659 1,4,16,50,130,296,610,1163,2083,3544,5776,9076,13820,20476,29618, %T A223659 41941,58277,79612,107104,142102,186166,241088,308914,391967,492871, %U A223659 614576,760384,933976,1139440,1381300,1664546,1994665,2377673,2820148,3329264 %N A223659 Number of unimodal maps [1..n]->[0..3]. %C A223659 Column 1 of A223663. %C A223659 Apparently also column 4 of A071920. - _R. J. Mathar_, May 17 2014 %H A223659 Alois P. Heinz, <a href="/A223659/b223659.txt">Table of n, a(n) for n = 0..10000</a> (terms n = 1..210 from R. H. Hardin) %H A223659 Kyu-Hwan Lee and Se-jin Oh, <a href="http://arxiv.org/abs/1601.06685">Catalan triangle numbers and binomial coefficients</a>, arXiv:1601.06685 [math.CO], 2016. %F A223659 Empirical: a(n) = (1/720)*n^6 + (1/48)*n^5 + (23/144)*n^4 + (9/16)*n^3 + (241/180)*n^2 + (11/12)*n + 1 = 1 + n*(n+1)*(n^4 + 14*n^3 + 101*n^2 + 304*n + 660)/720. %F A223659 Empirical g.f.: 1-x*(x^2-2*x+2)*(x^4-4*x^3+6*x^2-4*x+2) / (x-1)^7. - _R. J. Mathar_, May 14 2014 %e A223659 Some solutions for n=3: %e A223659 2 2 0 1 1 3 1 0 3 1 2 1 2 1 0 2 %e A223659 2 2 1 3 3 3 3 2 2 2 2 3 0 1 1 1 %e A223659 2 0 2 2 0 1 3 3 1 0 3 1 0 1 1 0 %Y A223659 Cf. A071920, A223663, A223718. %K A223659 nonn %O A223659 0,2 %A A223659 _R. H. Hardin_, Mar 25 2013 %E A223659 a(0)=1 prepended by _Alois P. Heinz_, Feb 11 2024