A107031 Diagonal sums of number triangle A107030.

1, 2, 3, 4, 7, 12, 25, 56, 145, 422, 1389, 5072, 20283, 87996, 412663, 2087868, 11361831, 66155642, 409567833, 2680486870, 18465061963, 133504614880, 1011121118741, 8008145020804, 66201411633209, 570006877641976

Offset: 0

Author

Paul Barry, May 09 2005

Keywords

• easy
• nonn

Formula

a(n)=sum{k=0..floor(n/2), (k-1)*C(k(n-2k), n-2k)-(k-2)*sum{j=0..n-k, C(k(n-2k), j)}}