A181893 Number of different nonnegative solutions of equation: x^2 - y^2 = k! for 1 <= k <= n.

1, 1, 1, 3, 7, 16, 34, 70, 130, 235, 445, 769, 1417, 2497, 4177, 6529, 11233, 17713, 30673, 49033, 76233, 119433, 205833, 316713, 471945, 715881, 1026345, 1449705, 2296425, 3376425, 5536425, 8128425, 11814825, 17528745, 25242537, 34480425, 52956201, 81509673

Offset: 1

Author

Artur Jasinski, Mar 31 2012

Keywords

• nonn

Crossrefs

Cf. A138196, A139151, A181892.

Programs

Mathematica

kkk = 1; cc = {1, 1, 1}; Do[w = n!/4; kk = Floor[(DivisorSigma[0, w] + 1)/2]; kkk = kkk + kk; AppendTo[cc, kkk], {n, 4, 54}]; cc

Formula

a(n)=sum(k=1..n, A138196(k) )