A138581 - OEIS

A138581

Numbers n such that 2^(2*n-15)-15 is prime.

8, 9, 10, 11, 19, 55, 125, 953

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OFFSET

1,1

LINKS

EXAMPLE

2^(2*11-15)-15=113, 2^(2*19-15)-15=8388593, 2^(2*55-15)-15=39614081257132168796771975153, ...

MATHEMATICA

q=15; For[i=q, i<=q, a={}; Do[x=2^(2*n-i)-i; If[PrimeQ[x], AppendTo[a, n]], {n, 10^2}]; Print["2^(2*n-", i, ")-", i, " ", a]; i=i+2]

Select[Range[1000], PrimeQ[2^(2#-15)-15]&] (* Harvey P. Dale, Jul 11 2023 *)

PROG

(PARI) is(n)=isprime(2^(2*n-15)-15) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

KEYWORD

nonn,easy

AUTHOR

EXTENSIONS

One more term (a(8)) from Harvey P. Dale, Jul 11 2023

STATUS

approved