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 A203653 #7 Jul 22 2025 17:25:13 %S A203653 59049,9616161,1780968921,343812029649,67213191427593, %T A203653 13192335511091073,2592476403527692089,509649251749126118193, %U A203653 100202323670442739140969,19701512822564218199726049,3873700712374667692894221465 %N A203653 1/25 the number of (n+1)X6 0..4 arrays with every 2X2 subblock having equal diagonal elements or equal antidiagonal elements. %C A203653 Column 5 of A203656 %H A203653 R. H. Hardin, <a href="/A203653/b203653.txt">Table of n, a(n) for n = 1..210</a> %F A203653 Empirical: a(n) = 249*a(n-1) -8592*a(n-2) -421104*a(n-3) +17434560*a(n-4) -117447936*a(n-5) -1126380544*a(n-6) +12165427200*a(n-7) -13434667008*a(n-8) -89049268224*a(n-9) +101291655168*a(n-10) +94447337472*a(n-11) -82896224256*a(n-12) %e A203653 Some solutions for n=4 %e A203653 ..1..0..0..2..4..1....3..0..4..1..1..2....0..4..0..2..3..2....1..2..4..4..4..4 %e A203653 ..1..1..0..0..2..4....1..3..0..4..1..1....0..0..3..0..2..1....1..1..2..4..1..4 %e A203653 ..1..4..1..0..0..2....4..1..3..0..4..1....2..0..0..0..0..2....1..0..1..2..4..4 %e A203653 ..1..1..0..2..0..0....0..4..1..3..0..4....3..2..0..3..0..0....4..1..2..0..2..4 %e A203653 ..4..1..1..0..3..0....4..0..4..1..3..0....4..3..2..0..1..0....1..4..1..2..2..2 %K A203653 nonn %O A203653 1,1 %A A203653 _R. H. Hardin_ Jan 04 2012