A089437 - OEIS

A089437

Numbers k such that 4^k + 3 is prime.

1, 2, 3, 6, 8, 9, 14, 15, 42, 114, 195, 392, 555, 852, 1004, 1185, 2001, 2030, 2031, 2276, 8610, 8967, 10362, 11366, 15927, 16514, 17877, 19122, 19898, 27728, 29156, 61275, 102981, 117663, 181560, 239922, 342789, 371226, 717200, 937776, 970406, 1102722

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OFFSET

1,2

COMMENTS

The halved even terms of A057732. - R. J. Mathar, Feb 26 2008

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

4^15 + 3 = 1073741827 a prime number.

PROG

(PARI) is(n)=ispseudoprime(4^n+3) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A057732, A228026 (the actual primes).

Sequence in context: A111215 A099381 A289943 * A146768 A364958 A211370

Adjacent sequences: A089434 A089435 A089436 * A089438 A089439 A089440

KEYWORD

nonn,more

AUTHOR

Herman H. Rosenfeld (herm3(AT)pacbell.net), Dec 28 2003

EXTENSIONS

More terms from Ray Chandler, Dec 30 2003

More terms from R. J. Mathar, Feb 26 2008

a(33)-a(37) derived from A057732 by Robert Price, Apr 26 2014

a(38)-a(42) derived from A057732 by Amiram Eldar, Nov 16 2023

STATUS

approved