OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Kevin A. Broughan and Zhou Qizhi, Flat primes and thin primes, Bulletin of the Australian Mathematical Society, Vol. 82, No. 2 (2010), pp. 282-292, alternative link.
FORMULA
a(n) ~ n log n.
MATHEMATICA
Select[Range[3, 200, 2], (r = (# + 1)/2^IntegerExponent[# + 1, 2]) == 1 || PrimeQ[r] &] (* Amiram Eldar, Aug 30 2020 *)
PROG
(PARI) is(n)=n%2&&(isprime((n+1)>>valuation(n+1, 2)) || n+1 == 1<<valuation(n+1, 2))&&n>1
CROSSREFS
KEYWORD
nonn
AUTHOR
Charles R Greathouse IV, Jul 11 2011
STATUS
approved