A247953 Numbers k such that 2^k + 33 is prime.

2, 3, 6, 11, 12, 14, 15, 20, 30, 60, 68, 75, 108, 116, 135, 206, 210, 410, 446, 558, 851, 1482, 1499, 2039, 2051, 4196, 7046, 7155, 8735, 10619, 18420, 20039, 46719, 75348, 179790, 203018, 434246

Offset: 1

Author

Vincenzo Librandi, Sep 28 2014

Keywords

• nonn
• more

Comments

Some terms correspond to probable primes. Lifchitz link shows the terms 179790 found by Donovan Johnson and 203018 by Lelio R Paula. - Jens Kruse Andersen, Sep 30 2014

a(38) > 5*10^5. - Robert Price, Nov 07 2015

Links

• Henri Lifchitz and Renaud Lifchitz, Search for 2^n+33, PRP Top Records.

Crossrefs

Cf. A094076, A176926, A247957.

Cf. Numbers k such that 2^k + d is prime: (0,1,2,4,8,16) for d=1; A057732 (d=3), A059242 (d=5), A057195 (d=7), A057196 (d=9), A102633 (d=11), A102634 (d=13), A057197 (d=15), A057200 (d=17), A057221 (d=19), A057201 (d=21), A057203 (d=23), A157006 (d=25), A157007 (d=27), A156982 (d=29), A247952 (d=31), this sequence (d=33), A220077 (d=35).

Programs

Magma

/* The code gives only the terms up to 851: */ [n: n in [1..1400]| IsPrime( 2^n + 33 )];

Maple

A247957:=n->`if`(isprime(2^n+33),n,NULL): seq(A247957(n), n=0..1000); # Wesley Ivan Hurt, Sep 28 2014

Mathematica

Select[Range[10000], PrimeQ[2^# + 33] &]

PARI

is(n)=ispseudoprime(2^n+33) \\ Charles R Greathouse IV, Feb 20 2017

Extensions

a(30)-a(34) from Jens Kruse Andersen, Sep 30 2014

a(35)-a(36) (discovered by Donovan Johnson and Lelio R Paula, respectively; see the Lifchitz link) added by Robert Price, Oct 04 2015

a(37) from Robert Price, Nov 07 2015