

A265482


Numbers n such that 16^n  4^n  1 is prime.


1



1, 2, 5, 9, 19, 25, 54, 104, 112, 120, 177, 317, 504, 540, 734, 780, 1649, 1923, 2715, 4308, 5917, 6494, 7305, 22653, 26888, 71448, 93834, 137027, 158472, 174648
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OFFSET

1,2


COMMENTS

For n = 1, 2, 5, 9, 19, 25, the corresponding primes are 11, 239, 1047551, 68719214591, 75557863725639445512191, 1267650600228228275596796362751.
a(n) is not of the form 5*k+6 (divisibility by 11) or 9*k+8 (divisibility by 19) or 7*k+3*(1)^k (divisibility by 29).
Conjecture: the odd terms are not of the form 8*k+7.
n is in the sequence iff 2*n is in A098845 (terms a(21)a(30) are derived from that sequence).  Ray Chandler, Sep 25 2019


LINKS



EXAMPLE

5 is in the sequence because 16^54^51 = 1047551 is prime.


MATHEMATICA

Select[Range[2500], PrimeQ[16^#  4^#  1] &]


PROG

(Magma) [n: n in [0..500]  IsPrime(16^n4^n1)];


CROSSREFS



KEYWORD

nonn,more


AUTHOR



STATUS

approved



