A350696 -id:A350696 - cp's OEIS frontend

1, 7, 7, 7, 91, 3103, 12451, 230191, 286867, 1657867, 10029811, 29761351, 22410151, 98402791, 167137543

Offset: 1

Mark Andreas, Jan 25 2023

a(n) == 3 (mod 4) for n > 1. - Chai Wah Wu, Jan 27 2023

			a(3) = 7 because 2^(2^3) + 7 = 263 is the smallest safe prime greater than 256.

a(n) = {my(k=1); pow2 = 2^(2^n);   while (!(isprime(pow2 + k) && isprime((pow2 + k - 1)/2)), k+=2); k;} \\

from sympy import isprime, nextprime
def A360080(n):
    if n <= 1: return 1
    m = 1<<(1<Chai Wah Wu, Jan 27 2023

a(n) = A350696(2^n).

3, 19, 31, 691, 907, 2887, 15943, 69283, 216127, 1108831, 8344423, 10976347, 166965391, 385465771, 26580643

Offset: 0

Mark Andreas, Jan 25 2023

a(n) == 3 (mod 4). - Chai Wah Wu, Jan 27 2023

			a(1) = 19 because 2^(3*2^1)+19 = 2^6+19 = 83 is the smallest safe prime greater than 64.

a(n) = {my(k=1); pow2 = 2^(3*2^n); while (!(isprime(pow2 + k) && isprime((pow2 + k - 1)/2)), k+=2); k;} \\

from sympy import isprime, nextprime
def A360081(n):
    m = 1<<3*(1<Chai Wah Wu, Jan 27 2023

a(n) = A350696(3*2^n).

cp's OEIS Frontend