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 A204245 #6 Jul 12 2012 00:39:59 %S A204245 1,1,4,84,9792,7015680,35334144000,1424547274752000, %T A204245 516934658477260800000,1875850653748811739955200000, %U A204245 74877948716953984356707205120000000,35866656974348638336845775173058560000000000 %N A204245 Determinant of the n-th principal submatrix of A204244. %t A204245 f[i_, j_] := 0; f[1, j_] := 1; f[i_, 1] := 1; f[i_, i_] := i!; %t A204245 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}] %t A204245 TableForm[m[8]] (* 8x8 principal submatrix *) %t A204245 Flatten[Table[f[i, n + 1 - i], %t A204245 {n, 1, 12}, {i, 1, n}]] (* A204244 *) %t A204245 Table[Det[m[n]], {n, 1, 15}] (* A204245 *) %t A204245 Permanent[m_] := %t A204245 With[{a = Array[x, Length[m]]}, %t A204245 Coefficient[Times @@ (m.a), Times @@ a]]; %t A204245 Table[Permanent[m[n]], {n, 1, 14}] (* A203228 *) %Y A204245 Cf. A204244, A203228. %K A204245 nonn %O A204245 1,3 %A A204245 _Clark Kimberling_, Jan 13 2012