A059511 Main diagonal of the array A059217.

1, 3, 26, 471, 13953, 627421, 39873948, 3406344237, 376591685322, 52319828460127, 8922977163384085, 1832831375530080986, 446306812127457163805, 127130280682997045232005, 41881054710966221044222595, 15800074329058136531647698779

Offset: 1

Author

Floor van Lamoen, Jan 21 2001

Keywords

• easy
• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..240

Programs

Mathematica

t[0, 0] = 1; t[0, ?EvenQ] = 1; t[?OddQ, 0] = 1; t[n_, k_] /; OddQ[n + k](*up*):= t[n, k] = t[n + 1, k - 1] + Sum[t[n, j], {j, 0, k - 1}];
t[n_, k_] /; EvenQ[n + k](*down*):= t[n, k] = t[n - 1, k + 1] + Sum[t[j, k], {j, 0, n - 1}]; Table[t[n, n], {n,0,50}] (* G. C. Greubel, Sep 10 2017 *)

Extensions

Terms a(11) onward added by G. C. Greubel, Sep 10 2017