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 A286933 #13 Mar 11 2025 02:55:17 %S A286933 1,1,0,1,1,0,1,2,1,0,1,3,4,2,0,1,4,9,12,3,0,1,5,16,36,32,5,0,1,6,25, %T A286933 80,135,88,9,0,1,7,36,150,384,513,248,15,0,1,8,49,252,875,1856,1971, %U A286933 688,26,0,1,9,64,392,1728,5125,9024,7533,1920,45,0,1,10,81,576,3087,11880,30125,43776,28836,5360,78,0 %N A286933 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of continued fraction 1/(1 - k*x/(1 - k*x^2/(1 - k*x^3/(1 - k*x^4/(1 - k*x^5/(1 - ...)))))). %H A286933 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Rogers-RamanujanContinuedFraction.html">Rogers-Ramanujan Continued Fraction</a> %F A286933 G.f. of column k: 1/(1 - k*x/(1 - k*x^2/(1 - k*x^3/(1 - k*x^4/(1 - k*x^5/(1 - ...)))))), a continued fraction. %F A286933 G.f. of column k (for k > 0): (Sum_{j>=0} (-k)^j*x^(j*(j+1))/Product_{i=1..j} (1 - x^i)) / (Sum_{j>=0} (-k)^j*x^(j^2)/Product_{i=1..j} (1 - x^i)). %e A286933 G.f. of column k: A(x) = 1 + k*x + k^2*x^2 + k^2*(k + 1)*x^3 + k^3*(k + 2)*x^4 + k^3*(k^2 + 3*k + 1)*x^5 + ... %e A286933 Square array begins: %e A286933 1, 1, 1, 1, 1, 1, ... %e A286933 0, 1, 2, 3, 4, 5, ... %e A286933 0, 1, 4, 9, 16, 25, ... %e A286933 0, 2, 12, 36, 80, 150, ... %e A286933 0, 3, 32, 135, 384, 875, ... %e A286933 0, 5, 88, 513, 1856, 5125, ... %t A286933 Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-k x^i, 1, {i, 1, n}]), {x, 0, n}]][j - n], {j, 0, 11}, {n, 0, j}] // Flatten %Y A286933 Columns k=0..1 give: A000007, A005169. %Y A286933 Rows n=0..3 give: A000012, A001477, A000290, A011379. %Y A286933 Main diagonal gives A291274. %Y A286933 Cf. A286932. %K A286933 nonn,tabl %O A286933 0,8 %A A286933 _Ilya Gutkovskiy_, May 16 2017