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A100663
Composite q such that 4^q + q is prime.
0
9, 15, 85, 133, 225, 1233, 12793, 108889
OFFSET
1,1
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
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