A112294 Diagonal sums of number triangle A112292.

1, 1, 4, 18, 121, 1055, 11376, 145852, 2165689, 36532197, 689873284, 14415662558, 330204013569, 8226714806323, 221470234531456, 6406397898751320, 198160750081637521, 6526636388676159977, 228040136335670652324

Offset: 0

Author

Paul Barry, Sep 01 2005

Keywords

• easy
• nonn

Formula

a(n)=sum{k=0..floor(n/2), (2n-2k-1)!!/(2k-1)!!}; a(n)=sum{k=0..floor(n/2), 2^(n-2k)(n-k-1/2)!/(k-1/2)!}; a(n)=sum{k=0..floor(n/2), (n-k)!C(2n-2k, n-k)2^(2k-n)/(k!C(2k, k))}; a(n)=sum{k=0..floor(n/2), (n-k+1)!*C(n-k)2^(2k-n)/((k+1)!*C(k))}.