A265683 - OEIS

A265683

Numbers n such that 16^n * (16^n - 1) - 1 is prime.

1, 27, 52, 56, 60, 252, 270, 367, 390, 2154, 3247, 13444, 35724, 46917, 79236, 87324

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OFFSET

1,2

COMMENTS

Each of the corresponding numbers of the form 16^n * (16^n - 1) - 1 is almost a repdigit in base 16 (i.e., a repdigit with only one change).

n is in the sequence iff 4*n is in A098845. - Robert Israel, Dec 14 2015

LINKS

Brady Haran and Simon Pampena, Glitch Primes and Cyclops Numbers, Numberphile video (2015)

MATHEMATICA

Select[Range[1000], PrimeQ[16^# (16^# - 1) - 1] &] (* _Shivam Patel_, Dec 13 2015 *)

PROG

(PARI) is(n)=ispseudoprime(16^n * (16^n - 1) - 1) \\ Anders Hellström, Dec 13 2015

(Magma) [n: n in [1..200] | IsPrime(256^n-16^n-1)]; // Vincenzo Librandi, Dec 14 2015

CROSSREFS

Cf. A098845, similar sequences listed in A265481.

KEYWORD

nonn,more

AUTHOR

EXTENSIONS

a(12)-a(16) computed from A098845 by Ray Chandler, Sep 25 2019

STATUS

approved