OFFSET
1,1
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section B43.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..14
M. Zivkovic, The number of primes sum_(i=1..n)(-1)^(n-i)i! is finite, Math. Comp., vol. 68 (1999), pp. 403-409.
MATHEMATICA
l = Abs@Accumulate[(-1)^#*#! & /@ Range@99]; l[[Flatten@Position[l, _?PrimeQ]]] (* Hans Rudolf Widmer, Feb 27 2023 *)
PROG
(PARI) for(n=1, 120, if(isprime(abs(sum(i=1, n, (-1)^i*i!)))==1, print1(abs(sum(i=1, n, (-1)^i*i!)), ", ")))
(PARI) v=[]; for(n=1, 1000, if(ispseudoprime(t=abs(sum(i=1, n, (-1)^i*i!))), v=concat(v, t))); v \\ Charles R Greathouse IV, Feb 14 2011
CROSSREFS
KEYWORD
nonn,fini
AUTHOR
Benoit Cloitre, Jun 08 2002
EXTENSIONS
Edited by R. J. Mathar, Aug 28 2007
STATUS
approved