A100663 Composite q such that 4^q + q is prime.

9, 15, 85, 133, 225, 1233, 12793, 108889

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Mathematica

For[n = 1, n < 5000, n++, If[Not[PrimeQ[n]], If[PrimeQ[4^n + n], Print[n]]]] (Steinerberger)
Select[Range[2, 10000], !PrimeQ[#]&&PrimeQ[4^#+#]&] (* Harvey P. Dale, Mar 09 2014 *)

Prog

(PARI) \\ p^q + q is prime q not prime
ptoqpq(p, n)= { local(x, y, q); for(q=6, n, if(q%2, if(!isprime(q), y=p^q+q; if(ispseudoprime(y), print1(q", ")) ) ) ) }

Crossrefs

Composites in A057909.

Sequence in context: A043917 A351499 A037378 * A304457 A219129 A226927

Adjacent sequences: A100660 A100661 A100662 * A100664 A100665 A100666

Keyword

nonn,more

Author

Cino Hilliard, Jan 12 2005

Extensions

a(6) from Stefan Steinerberger, Jan 27 2006

a(7)-a(8) using A057909 from Michael S. Branicky, Jun 28 2024

Status

approved