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 A223673 #6 Jul 23 2025 04:22:36 %S A223673 64,4096,61996,321163,1023339,2715255,6789502,16634224,40086061, %T A223673 94218637,214377471,470774847,998649425,2051656863,4092563126, %U A223673 7942987666,15025087905,27743027247,50072239147,88451496245,153108327757 %N A223673 Number of 6Xn 0..1 arrays with rows, diagonals and antidiagonals unimodal. %C A223673 Row 6 of A223669 %H A223673 R. H. Hardin, <a href="/A223673/b223673.txt">Table of n, a(n) for n = 1..129</a> %F A223673 Empirical: a(n) = (271/5443200)*n^12 - (5527/1995840)*n^11 + (284203/2721600)*n^10 - (97799/51840)*n^9 - (4335667/259200)*n^8 + (68712079/30240)*n^7 - (50002254419/680400)*n^6 + (495395854627/362880)*n^5 - (42767475646507/2721600)*n^4 + (1367715597167/12960)*n^3 - (3261545344751/10800)*n^2 - (3687840940699/6930)*n + 4224261488 for n>20 %e A223673 Some solutions for n=4 %e A223673 ..0..0..1..0....0..0..0..0....0..0..0..1....0..0..0..1....0..0..0..0 %e A223673 ..0..1..0..0....0..0..0..0....0..1..1..0....0..1..1..0....0..0..0..0 %e A223673 ..0..0..1..0....1..0..0..0....1..1..1..1....0..1..1..0....0..1..0..0 %e A223673 ..0..0..0..1....0..0..0..0....1..1..1..1....1..1..0..0....1..0..0..0 %e A223673 ..0..1..1..1....0..1..0..0....1..1..1..0....0..0..0..0....0..1..0..0 %e A223673 ..0..1..1..1....0..0..0..0....1..1..1..0....0..0..0..0....0..0..0..0 %K A223673 nonn %O A223673 1,1 %A A223673 _R. H. Hardin_ Mar 25 2013