

A192868


Thin numbers: odd numbers k > 1 such that k+1 is a prime times a power of two.


3



3, 5, 7, 9, 11, 13, 15, 19, 21, 23, 25, 27, 31, 33, 37, 39, 43, 45, 47, 51, 55, 57, 61, 63, 67, 73, 75, 79, 81, 85, 87, 91, 93, 95, 103, 105, 111, 115, 117, 121, 123, 127, 133, 135, 141, 145, 147, 151, 157, 159, 163, 165, 171, 175, 177, 183, 187, 191, 193
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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. 282292, 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

Cf. A192869.
Sequence in context: A204458 A192861 A333854 * A283553 A081110 A143449
Adjacent sequences: A192865 A192866 A192867 * A192869 A192870 A192871


KEYWORD

nonn


AUTHOR

Charles R Greathouse IV, Jul 11 2011


STATUS

approved



