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 A054975 #12 Jul 02 2025 16:01:59 %S A054975 1,3,13,38,97,217,453,868,1585,2756,4606,7440,11679,17849,26674,39060, %T A054975 56144,79387,110575,151904,206063,276332,366561,481484,626586,808431, %U A054975 1034636,1314242,1657500,2076601,2585262,3199504,3937370,4819788 %N A054975 Number of nonnegative integer 3 X 3 matrices with no zero rows or columns and with sum of elements equal to n, up to row and column permutation. %H A054975 Andrew Howroyd, <a href="/A054975/b054975.txt">Table of n, a(n) for n = 3..1000</a> %F A054975 G.f.: x^3*(x^14 - 2*x^13 + x^12 - 3*x^11 + 4*x^10 - 3*x^9 + 4*x^8 - x^7 - 4*x^6 + 2*x^5 - x^4 - 5*x^3 - 4*x^2 - 1)/((x^4 - x^3 + x - 1)*(x^3 - 1)^3*(x + 1)^3*(x - 1)^5). %e A054975 There are 3 nonnegative integer 3 X 3 matrices with no zero rows or columns and with sum of elements equal to 4, up to row and column permutation: %e A054975 [0 0 1] [0 0 1] [0 0 1] %e A054975 [0 0 1] [0 1 0] [0 1 0] %e A054975 [1 1 0] [1 0 1] [2 0 0]. %p A054975 gf := x^3*(x^14 - 2*x^13 + x^12 - 3*x^11 + 4*x^10 - 3*x^9 + 4*x^8 - x^7 - 4*x^6 + 2*x^5 - x^4 - 5*x^3 - 4*x^2 - 1)/((x^4 - x^3 + x - 1)*(x^3 - 1)^3*(x+1)^3*(x - 1)^5): s := series(gf, x, 101): for i from 3 to 100 do printf(`%d,`,coeff(s,x,i)) od: %Y A054975 Column k=3 of A321615. %Y A054975 Cf. A052365. %K A054975 easy,nonn %O A054975 3,2 %A A054975 _Vladeta Jovovic_, May 28 2000 %E A054975 More terms from _James Sellers_, May 29 2000