A138599 Numbers k such that 2^(2*k-31) - 31 is prime.

19, 21, 22, 24, 25, 33, 34, 36, 46, 49, 60, 70, 90, 93, 112, 137, 143, 207, 216, 263, 280, 477, 647, 1257, 1383, 1686, 2952, 3234, 3919, 5703, 7705, 10077, 15312, 17049, 17261, 27828, 47626, 49663, 52626

Offset

1,1

Links

Table of n, a(n) for n=1..39.

Example

2^(2*19-31)-31 = 97, 2^(2*21-31)-31 = 2017, 2^(2*22-31)-31 = 8161, ... .

Mathematica

q=31; For[i=q, i<=q, a={}; Do[x=2^(2*n-i)-i; If[PrimeQ[x], AppendTo[a, n]], {n, 20^2}]; Print["2^(2*n-", i, ")-", i, " ", a]; i=i+2]
Select[Range[1500], PrimeQ[2^(2#-31)-31]&]

Prog

(PARI) is(n)=isprime(2^(2*n-31)-31) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

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

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

Sequence in context: A042735 A156758 A089837 * A020347 A334103 A347343

Adjacent sequences: A138596 A138597 A138598 * A138600 A138601 A138602

Keyword

nonn,more

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

More terms from Harvey P. Dale, Apr 08 2018

Terms 16 and 17 removed and a(26)-a(39) from Michael S. Branicky, May 21 2026

Status

approved