OFFSET
0,2
COMMENTS
If it exists, a(63) > 10000.
EXAMPLE
a(0) = 1: 2^1 - 2^0 + 1 = 2 = A331205(0) is prime,
a(1) = 2: 2^2 - 2^1 + 1 = 3 = A331205(1) is prime,
a(2) = 3: 2^3 - 2^2 + 1 = 5 = A331205(2) is prime,
a(3) = 39: 2^39 - 2^3 + 1 = 549755813881 = A331205(3) is prime, whereas all smaller values of m give composite sums: 9, 25, 57, 121, 249, 505, ..., 274877906937.
PROG
(PARI) for(n=0, 62, for(m=n+1, oo, k=2^m-2^n+1; if(isprime(k), print1(m, ", "); break)))
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Hugo Pfoertner, Jan 12 2020
STATUS
approved