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 A213963 #8 Jul 22 2025 23:05:09 %S A213963 138,3186,32060,199735,909900,3323712,10301232,28115505,69342790, %T A213963 157454154,333771516,667605263,1270560760,2316187440,4066346688, %U A213963 6905893425,11387501154,18288711250,28683554460,44031375927,66285794564 %N A213963 Number of 3X3 0..n matrices with row and column 1..3 having sum <= i*n. %C A213963 Row 3 of A213962 %H A213963 R. H. Hardin, <a href="/A213963/b213963.txt">Table of n, a(n) for n = 1..210</a> %F A213963 Empirical: a(n) = (n+3) *(n+2) *(449*n^5+3038*n^4+7759*n^3+9790*n^2+6264*n+1680) *(1+n)^2/10080. %e A213963 Some solutions for n=4 %e A213963 ..2..0..0....4..0..0....4..0..0....2..0..0....0..3..0....2..2..0....1..3..0 %e A213963 ..0..0..0....0..1..2....0..2..4....0..2..2....2..1..2....2..2..2....1..4..2 %e A213963 ..1..4..2....0..0..1....0..3..3....0..3..1....2..4..0....0..4..3....0..1..0 %K A213963 nonn %O A213963 1,1 %A A213963 _R. H. Hardin_ Jun 28 2012