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A276660
Primes of the form p*2^k - 1 where p is an odd prime and k >= 0.
0
2, 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, 1123
OFFSET
1,1
FORMULA
a(n) >> n (log n)^2. - Charles R Greathouse IV, Sep 11 2016
EXAMPLE
2 is in this sequence because 3*2^0 - 1 = 2 is prime.
5 is in this sequence because 3*2^1 - 1 = 5 is prime.
11 is in this sequence because 3*2^2 - 1 = 11 is prime.
PROG
(PARI) is(n)=isprime((n+1)>>valuation(n+1, 2)) && isprime(n) \\ Charles R Greathouse IV, Sep 11 2016
CROSSREFS
Essentially the same as A192869 and A206581.
Sequence in context: A191048 A105961 A045361 * A086081 A345707 A113305
KEYWORD
nonn
AUTHOR
STATUS
approved