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A367186
Numbers that can be written as 2^k + prime in more than one way.
1
4, 6, 7, 9, 11, 13, 15, 18, 19, 21, 23, 25, 27, 31, 33, 35, 37, 39, 43, 45, 47, 49, 51, 55, 57, 61, 63, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 91, 93, 95, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 121, 123, 125, 129, 131, 133, 135, 139, 141, 143, 145, 147, 151, 153, 155
OFFSET
1,1
COMMENTS
Numbers m such that A109925(m) > 1.
EXAMPLE
4 is a term since 4 = 2^0 + 3 = 2^1 + 2 which is 2 ways.
6 is a term since 6 = 2^0 + 5 = 2^2 + 2.
PROG
(PARI) isok(m) = sum(k=0, logint(m, 2), isprime(m-2^k)) > 1; \\ Michel Marcus, Nov 10 2023
(Python)
from itertools import count, islice
from sympy import isprime
def A367186_gen(startvalue=1): # generator of terms >= startvalue
for n in count(max(startvalue, 1)):
c = 0
for i in range(n.bit_length()-1, -1, -1):
if isprime(n-(1<<i)):
c+=1
if c>1:
yield n
break
A367186_list = list(islice(A367186_gen(), 30)) # Chai Wah Wu, Nov 29 2023
CROSSREFS
Subsequence of A118955.
Sequence in context: A186497 A193627 A256792 * A345665 A343177 A085817
KEYWORD
nonn
AUTHOR
Yuda Chen, Nov 08 2023
STATUS
approved