OFFSET
1,2
EXAMPLE
a(5)=2 because for n=5: 4*5*2+1=41 is a prime.
PROG
(PARI) a(n) = my(k = 0); while (! isprime(4*n*k+1), k++); k; \\ Michel Marcus, Sep 28 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Erich Friedman
STATUS
approved