A138580 Numbers k such that 2^(2*k-13) - 13 is prime.

9, 11, 13, 15, 35, 59, 75, 1615, 1621, 2123, 3055, 4385, 5735, 6043, 7719, 20065, 22685

Offset

1,1

Comments

a(18) > 60000. - Michael S. Branicky, May 20 2026

Links

Table of n, a(n) for n=1..17.

Example

2^(2*11-13)-13 = 499, 2^(2*13-13)-13 = 8179, 2^(2*15-13)-13 = 131059, ... .

Mathematica

q=13; 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-13)-13) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

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

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

Sequence in context: A251394 A155877 A214865 * A373627 A225557 A120177

Adjacent sequences: A138577 A138578 A138579 * A138581 A138582 A138583

Keyword

nonn,more

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

Terms 7 and 8 removed and a(8)-a(17) from Michael S. Branicky, May 20 2026

Status

approved