1,1

Note that when n is even, 3 divides the sum.

The sums corresponding to terms >= 661 are only probable primes. - Klaus Brockhaus, Mar 13 2009

Table of n, a(n) for n=1..15.

a(2)=((-1)^0)(2-0)!+((-1)^1)(2-1)!+((-1)^2)(2-2)!+1=2!-1!+0!+1= 3 (prime).

Sequence in context: A303875 A331037 A228652 * A175758 A151531 A079987

Adjacent sequences: A157830 A157831 A157832 * A157834 A157835 A157836

nonn

Kyle D. Balliet, Mar 07 2009

a(7) - a(15) from Klaus Brockhaus, Mar 13 2009

approved