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A318294 Prime-indexed primes p such that 2*p + 1 is also a prime-indexed prime. 0
5, 41, 1031, 3299, 3761, 6323, 7649, 7841, 10589, 12959, 18443, 37853, 38039, 44729, 58511, 59723, 60509, 77813, 105971, 134489, 137999, 190523, 194933, 200351, 239633, 250751, 266093, 288653, 315011, 366161, 376241, 377633, 393401, 410999, 420419, 420779, 450431, 474983 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Prime-indexed Sophie Germain primes whose associated safe primes are also prime-indexed. Subsequence of A005384.

LINKS

Table of n, a(n) for n=1..38.

N. Fernandez, An order of primeness, F(p)

N. Fernandez, An order of primeness [cached copy, included with permission of the author]

EXAMPLE

5 = prime(3) is a prime-indexed prime, and 2*5 + 1 = 11 = prime(5) is also a prime-indexed prime. Therefore 5 is in the sequence.

3 = prime(2) is a prime-indexed prime, but 2*3 + 1 = 7 = prime(4) is not a prime-indexed prime since 4 is composite. Therefore 3 is not in the sequence.

PROG

(PARI) isok(p) = isprime(p) && isprime(primepi(p)) && isprime(2*p+1) && isprime(primepi(2*p+1)); \\ Michel Marcus, Aug 28 2018

CROSSREFS

Cf. A005384, A006450.

Sequence in context: A189997 A197173 A052113 * A093433 A065035 A145008

Adjacent sequences:  A318291 A318292 A318293 * A318295 A318296 A318297

KEYWORD

nonn

AUTHOR

David James Sycamore, Aug 23 2018

EXTENSIONS

More terms from Michel Marcus, Aug 28 2018

STATUS

approved

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Last modified August 8 19:29 EDT 2020. Contains 336298 sequences. (Running on oeis4.)