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A160600
Numbers n such that 3*(2n)^(2n)+1 is prime.
4
1, 2, 3, 5, 143, 225
OFFSET
1,2
COMMENTS
This corresponds to the numbers such that 3m^m+1 is prime, but these must all be even, m=2n, and therefore it is more natural to record the sequence of n=m/2.
Next term > 15000. - Matevz Markovic, Oct 09 2012
EXAMPLE
a(1) = 1, because 2^2*3+1 = 13 is the smallest prime of this form.
a(2) = 2, because 4^4*3+1 = 769 is the next smallest prime of this form. a(3) = 3, because 6^6*3+1 = 139969 is again a prime.
PROG
(PARI) for(i=1, 9999, ispseudoprime(i^i*3+1)&print1(i/2, ", "))
CROSSREFS
Cf. A160360 (3n^n+2 is prime), A121270 = primes among Sierpinski numbers A014566(n)=n^n+1; A216148 = A216147(A110932): primes 2n^n+1; A088790, A065798.
Sequence in context: A117702 A041343 A229349 * A325505 A366642 A319609
KEYWORD
hard,more,nonn
AUTHOR
M. F. Hasler, Jul 10 2009
STATUS
approved