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

16, 17, 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

Offset

1,1

Links

Table of n, a(n) for n=1..27.

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

Sequence in context: A209726 A326455 A145449 * A258265 A261344 A007636

Adjacent sequences: A138596 A138597 A138598 * A138600 A138601 A138602

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

More terms from Harvey P. Dale, Apr 08 2018

Status

approved