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A144360 Primes of the form 8^k + 7. Also, primes of the form 64^m + 7. 9
71, 262151, 1073741831, 302231454903657293676551, 85070591730234615865843651857942052871, 23945242826029513411849172299223580994042798784118791, 25711008708143844408671393477458601640355247900524685364822023 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

k=2m, since for odd k, 8^k + 7 is divisible by 3.

Prime numbers p in A144242 such that p-1 is the fourth a-gonal and seventh b-gonal number for some a and b. Namely, a = (8^k+14)/6 and b = (8^k + 41)/21.

This sequence appears to be a subset of A144313.

The next term has 178 digits. - Harvey P. Dale, Sep 03 2015

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

71 - 1 = 70 is the fourth triskaidecagonal number and seventh pentagonal number.

MATHEMATICA

Select[64^Range[40]+7, PrimeQ] (* Harvey P. Dale, Sep 03 2015 *)

PROG

(MAGMA) [a: n in [0..80] | IsPrime(a) where a is 8^n+7]; // Vincenzo Librandi, Aug 02 2017

CROSSREFS

Cf. A000040, A000668, A144231, A144232, A144233, A144234, A144236, A144242, A144245, A144246, A144247, A144313

Sequence in context: A099684 A078915 A144242 * A230378 A093176 A057384

Adjacent sequences:  A144357 A144358 A144359 * A144361 A144362 A144363

KEYWORD

nonn

AUTHOR

Reikku Kulon, Sep 18 2008

EXTENSIONS

Edited by Max Alekseyev, Feb 17 2011

STATUS

approved

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Last modified April 18 22:08 EDT 2019. Contains 322237 sequences. (Running on oeis4.)