A206581 Odd primes p such that p+1 is a prime times a power of two.

5, 11, 13, 19, 23, 37, 43, 47, 61, 67, 73, 79, 103, 151, 157, 163, 191, 193, 211, 223, 271, 277, 283, 313, 331, 367, 383, 397, 421, 457, 463, 487, 523, 541, 547, 607, 613, 631, 661, 673, 691, 733, 751, 757, 787, 823, 877, 907, 991, 997, 1051, 1087, 1093

Offset

1,1

Comments

Very similar to A192869; here p+1 = q*2^k, where q must be prime.

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Kevin Broughan and Zhou Qizhi, Flat primes and thin primes, Bulletin of the Australian Mathematical Society 82:2 (2010), pp. 282-292.

Formula

a(n) >> n log^2 n is implicit in Broughan & Qizhi, see A192869. - Charles R Greathouse IV, Sep 15 2015

Mathematica

Select[Prime[Range[2, 1000]], PrimeQ[(#+1)/2^IntegerExponent[#+1, 2]] &]

Prog

(PARI) is(n)=isprime(n) && n>4 && isprime((n+1)>>valuation(n+1, 2)) \\ Charles R Greathouse IV, Sep 15 2015

Crossrefs

Subsequence of A192869.

Sequence in context: A340466 A222219 A023225 * A292940 A098085 A104216

Adjacent sequences: A206578 A206579 A206580 * A206582 A206583 A206584

Keyword

nonn

Author

T. D. Noe, Mar 07 2012

Status

approved