A323216 Main diagonal of A323212.

1, 1, 7, 56, 477, 4180, 37401, 339184, 3107583, 28691938, 266537777, 2488340790, 23326071990, 219416722056, 2070014554612, 19578402111888, 185583671757949, 1762564846962972, 16768616366059543, 159777503753057786, 1524516616304476102, 14564266581096857240

Offset: 0

Author

Peter Luschny, Mar 18 2019

Keywords

• nonn

Crossrefs

A323212.

Programs

Mathematica

nmax = 21; T = PadRight[CoefficientList[# + O[y]^(nmax+1), y], nmax+1]& /@ CoefficientList[1 + 2 x (x+1)/(Sqrt[1 - 4 y] - 2 x (x+1) + 1) + O[x]^(nmax+1), x];
a[n_] := T[[n + 1, n + 1]];
Table[a[n], {n, 0, nmax}] (* Jean-François Alcover, Jul 21 2019 *)