A059511 - OEIS

%I #9 Sep 10 2017 15:04:02

%S 1,3,26,471,13953,627421,39873948,3406344237,376591685322,

%T 52319828460127,8922977163384085,1832831375530080986,

%U 446306812127457163805,127130280682997045232005,41881054710966221044222595,15800074329058136531647698779

%N Main diagonal of the array A059217.

%H G. C. Greubel, <a href="/A059511/b059511.txt">Table of n, a(n) for n = 1..240</a>

%t 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 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 *)

%K easy,nonn

%O 1,2

%A _Floor van Lamoen_, Jan 21 2001

%E Terms a(11) onward added by _G. C. Greubel_, Sep 10 2017