OFFSET
1,2
COMMENTS
Primes p present are those that occur as factors of (2^A000720(p))-1: 3, 43, 49477, 4394113, 33228911, ...
LINKS
EXAMPLE
1177 = 11 * 107, with A243071(1177) = 536870895 = 3*5*11*47*107*647, therefore 1177 is present. Note that 536870895 = 11111111111111111111111101111 in binary, with four 1-bits at the least significant end, followed by 0, and then 24 more 1-bits at the most significant end, so A163511(536870895) = A000040(1+4) * A000040(4+24) = 11 * 107.
PROG
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Antti Karttunen, Jul 27 2023
EXTENSIONS
a(10) from Chai Wah Wu, Jul 27 2023
STATUS
approved