A059227 Last entry in n-th row of triangle defined in A059226.

1, 1, 4, 18, 94, 544, 3370, 21878, 146924, 1012222, 7114218, 50808592, 367669254, 2689974234, 19864822564, 147875395930, 1108469655350, 8359790718480, 63387403235682, 482935966313310, 3695204342149004, 28383451250732662

Offset: 0

Author

N. J. A. Sloane, Jan 19 2001

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..250
• Index entries for sequences related to boustrophedon transform

Programs

Mathematica

T[i_, j_] := T[i, j] = Module[{r, s, t1}, If[i == 0 && j == 0,Return[1]];
If[j == 0, Return[0]]; t1 = T[i, j - 1]; For[r = 0, r <= i - j, r++,
For[s = 0, s <= j, s++, If[r + s != i, t1 = t1 + T[r + s, s]]]];
Return[t1]]; Table[T[n, n], {n, 0, 25}] (* G. C. Greubel, Jan 03 2017 *)
Join[{1}, CoefficientList[Nest[1+(3x-x^2)#+(x-x^2)#^2&, 1+O[x], 20], x]] (* Oliver Seipel, Dec 28 2024 *)