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 A204261 #6 Jul 12 2012 00:39:59
%S A204261 1,2,13,104,1357,22052,555325,17622590,680239111,31511481788,
%T A204261 1717710101869,109014509616567,8596454332733239,783330147715515842,
%U A204261 79369033657791374935,9105430313767018411610
%N A204261 Permanent of the n-th principal submatrix of A204260.
%t A204261 f[i_, j_] := Ceiling[i*j/(i + j)];
%t A204261 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
%t A204261 TableForm[m[8]] (* 8x8 principal submatrix *)
%t A204261 Flatten[Table[f[i, n + 1 - i],
%t A204261 {n, 1, 12}, {i, 1, n}]] (* A204260 *)
%t A204261 Permanent[m_] :=
%t A204261 With[{a = Array[x, Length[m]]},
%t A204261 Coefficient[Times @@ (m.a), Times @@ a]];
%t A204261 Table[Permanent[m[n]], {n, 1, 14}] (* A204261 *)
%Y A204261 Cf. A204260.
%K A204261 nonn
%O A204261 1,2
%A A204261 _Clark Kimberling_, Jan 14 2012