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%I #17 Jun 28 2024 12:12:20
%S 9,15,85,133,225,1233,12793,108889
%N Composite q such that 4^q + q is prime.
%t For[n = 1, n < 5000, n++, If[Not[PrimeQ[n]], If[PrimeQ[4^n + n], Print[n]]]] (Steinerberger)
%t Select[Range[2,10000],!PrimeQ[#]&&PrimeQ[4^#+#]&] (* _Harvey P. Dale_, Mar 09 2014 *)
%o (PARI) \\ p^q + q is prime q not prime
%o 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",")) ) ) ) }
%Y Composites in A057909.
%K nonn,more
%O 1,1
%A _Cino Hilliard_, Jan 12 2005
%E a(6) from _Stefan Steinerberger_, Jan 27 2006
%E a(7)-a(8) using A057909 from _Michael S. Branicky_, Jun 28 2024
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