A263865 Odd k for which abs(2^m - k) is nonprime for all m < k.

1, 337, 2293, 4327, 6247, 6269, 12749, 13603, 14023, 14347, 14407, 15997, 21673, 25229, 31511, 36971, 47107, 48703, 48959, 50171, 56351, 59399, 63389, 69427, 83381, 84491, 85061, 104549, 107857, 109649, 118567

Offset: 1

Author

Arkadiusz Wesolowski, Oct 28 2015

Keywords

• nonn
• more

Comments

Related to the problem in A076337.

Crossrefs

Cf. A076337, A101036.

Programs

PARI

forstep(k=1, 6269, 2, c=m=0; while(m
				

Python

from gmpy2 import is_prime
def ok(k): return k&1 and all(not is_prime(abs((1<Michael S. Branicky, May 22 2025

Extensions

a(20)-a(31) from Michael S. Branicky, May 22 2025