OFFSET
1,1
COMMENTS
The 1 < k part of the condition in the definition is implied by Wilson's theorem.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..719
EXAMPLE
c = 25 satisfies the congruence with k = 21, since ((25-21)!+1) mod 25 = 0, so 25 is a term of the sequence.
PROG
(PARI) forcomposite(c=1, , for(k=1, c-1, if(Mod((c-k)!, c)==-1, print1(c, ", "); break({1}))))
(PARI) is(n)=if(isprime(n), return(0)); my(m=Mod(6, n)); for(k=4, n, m*=k; if(m==-1, return(1)); if(gcd(m, n)!=1, return(0))) \\ Charles R Greathouse IV, Apr 02 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Apr 01 2015
EXTENSIONS
a(25)-a(36) from Charles R Greathouse IV, Apr 02 2015
STATUS
approved