A144360 Primes of the form 8^k + 7. Also, primes of the form 64^m + 7.

71, 262151, 1073741831, 302231454903657293676551, 85070591730234615865843651857942052871, 23945242826029513411849172299223580994042798784118791, 25711008708143844408671393477458601640355247900524685364822023

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 * A350005 A230378 A352732

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