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 A223685 #6 Jul 23 2025 04:23:47 %S A223685 128,16384,537496,6458585,43632367,210660192,821284360,2758051780, %T A223685 8275194605,22704480123,57880672236,138698869116,315159317570, %U A223685 683706718357,1423847390903,2859216983489,5556849891974,10484853235610 %N A223685 Number of 7Xn 0..1 arrays with rows and antidiagonals unimodal. %C A223685 Row 7 of A223680 %H A223685 R. H. Hardin, <a href="/A223685/b223685.txt">Table of n, a(n) for n = 1..210</a> %F A223685 Empirical: a(n) = (503/209563200)*n^14 + (6527/155675520)*n^13 + (68839/23950080)*n^12 + (1220297/59875200)*n^11 + (1890089/2177280)*n^10 + (181499/362880)*n^9 + (1367211271/15240960)*n^8 - (1887455579/5443200)*n^7 + (43827922247/10886400)*n^6 - (12546180643/544320)*n^5 + (1259322375259/11975040)*n^4 - (234159554591/554400)*n^3 + (13743908156557/11642400)*n^2 - (52010645243/24024)*n + 1969115 for n>4 %e A223685 Some solutions for n=3 %e A223685 ..0..0..0....0..0..1....0..0..1....0..0..0....0..0..1....0..0..0....0..0..0 %e A223685 ..0..1..1....0..0..1....0..0..1....0..1..1....0..0..1....0..1..1....0..0..0 %e A223685 ..1..1..0....0..1..0....0..1..1....0..0..0....0..0..0....1..1..0....1..1..0 %e A223685 ..1..1..1....0..0..1....0..1..1....0..1..0....0..1..0....0..0..0....0..1..0 %e A223685 ..0..1..0....1..1..1....1..1..0....1..1..0....0..1..1....1..1..0....0..1..0 %e A223685 ..0..1..0....1..1..0....1..0..0....1..1..0....0..0..1....0..0..0....1..1..0 %e A223685 ..0..0..1....0..0..0....0..0..0....0..1..1....0..0..0....0..1..1....0..0..0 %K A223685 nonn %O A223685 1,1 %A A223685 _R. H. Hardin_ Mar 25 2013