A100018 a(n) is the least k such that k*2^n*(2^n-1)-1 and k*2^n*(2^n-1)+1 are twin primes.

2, 1, 48, 1, 30, 25, 33, 12, 30, 6, 117, 22, 471, 119, 255, 98, 180, 29, 153, 48, 399, 135, 267, 20, 426, 320, 213, 391, 714, 216, 1395, 148, 915, 65, 2703, 65, 525, 364, 573, 173, 240, 1239, 657, 205, 135, 30, 1080, 82, 1056, 604, 3102, 148, 279, 661, 1962, 435, 306

Offset

1,1

Links

Table of n, a(n) for n=1..57.

Example

2*2^1*(2^1-1)-1 = 3 and 2*2^1*(2^1-1)+1 = 5, 3 and 5 twin primes so a(1)=2.

Prog

(PARI) a(n) = my(k=1); while(!(isprime(k*2^n*(2^n-1)-1) && isprime(k*2^n*(2^n-1)+1)), k++); k; \\ Michel Marcus, Jan 31 2023

Crossrefs

Sequence in context: A308749 A260884 A214221 * A255856 A037056 A358857

Adjacent sequences: A100015 A100016 A100017 * A100019 A100020 A100021

Keyword

nonn

Author

Pierre CAMI, Nov 19 2004

Extensions

Name edited by Michel Marcus, Jan 31 2023

Status

approved