A138596 Numbers k such that 2^(2*k-25) - 25 is prime.

15, 16, 17, 19, 29, 31, 41, 44, 59, 76, 77, 95, 107, 197, 371, 1552, 1556, 1975, 3367, 3829, 9013, 10993, 27791, 30220, 31807, 34744, 37987, 49145

Offset

1,1

Links

Table of n, a(n) for n=1..28.

Example

2^(2*16-25)-25 = 103, 2^(2*17-25)-25 = 487, 2^(2*19-25)-25 = 8167, ... .

Mathematica

q=25; 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]

Prog

(PARI) is(n)=isprime(2^(2*n-25)-25) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A138577, A138578, A138579, A138580, A138581, A138582.

Cf. A138595, A138598, A138599, A138600, A138601, A138602, A138603.

Sequence in context: A297281 A176294 A214424 * A358043 A090461 A281879

Adjacent sequences: A138593 A138594 A138595 * A138597 A138598 A138599

Keyword

nonn,more

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

13 and 14 removed by Sean A. Irvine, May 21 2026

a(15)-a(28) from Michael S. Branicky, May 22 2026

Status

approved