A174662 Partial sums of A003149.

1, 3, 8, 24, 88, 400, 2212, 14500, 110116, 951076, 9205156, 98646436, 1159016356, 14808626596, 204358994596, 3028436306596, 47955883346596, 807990334802596, 14430691329362596, 272302801683794596, 5412861968581970596

Offset: 0

Author

Jonathan Vos Post, Nov 30 2010

Keywords

• nonn
• easy

Comments

Total resistance of a circuit whose n-th component is between opposite corners of an n-dimensional hypercube of unit resistors, multiplied by n!. The only prime in the sequence is 3. The subsequence of squares begins 1, 400, 9205156 = 2^2 * 37^2 * 41^2.

Examples

			a(5) = 1 + 2 + 5 + 16 + 64 + 312 = 400 = 2^4 * 5^2.
		

Crossrefs

Cf. A003149, A046825, A046878, A046879, A052186, A006932, A145878.

Formula

a(n) = Sum_{i=0..n} Sum_{k=0..i} k!*(i-k)!.

Extensions

Offset set to 0 by Alois P. Heinz, Jun 28 2017