OFFSET
1,3
COMMENTS
a(n) = 1 iff n+1 is prime.
If a(n) = 0, then n is in A097792. Note that the converse is not true: a(4) = 1, not 0.
EXAMPLE
3*1^3+1 = 4 is not prime. 3*2^3+1 = 25 is not prime. 3*3^3+1 = 82 is not prime. 3*4^3+1 = 193 is prime. Thus, a(3) = 4.
PROG
(PARI) Pf(n) = for(k=1, 10^4, if(ispseudoprime(n*k^n+1), return(k))); n=1; while(n<50, print(Pf(n)); n+=1)
CROSSREFS
KEYWORD
nonn
AUTHOR
Derek Orr, Mar 29 2014
STATUS
approved