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A057221 Numbers n such that 2^n + 19 is prime. 8
2, 6, 30, 162, 654, 714, 1370, 1662, 1722, 2810, 77142, 156254, 432974 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(14) > 5*10^5. - Robert Price, Aug 27 2015

All terms are even. - Robert Israel, Aug 28 2015

For numbers n in this sequence, the number 2^(n-1)*(2^n+19) has deficiency 20, cf. A223607. - M. F. Hasler, Jul 18 2016

LINKS

Table of n, a(n) for n=1..13.

H. Lifchitz & R. Lifchitz (Editors), PRP Top Records, of the form 2^n+19.

FORMULA

a(n) = 2 * A253774(n). - Joerg Arndt, Aug 28 2015

MAPLE

select(n -> isprime(2^n+19), [seq(2*i, i=1..10000)]); # Robert Israel, Aug 28 2015

MATHEMATICA

Do[ If[ PrimeQ[ 2^n + 19 ], Print[ n ] ], {n, 1, 15000} ]

Select[Range[10000], PrimeQ[2^# + 19] &] (* Vincenzo Librandi, Aug 28 2015 *)

PROG

(MAGMA) [n: n in [0..1000] | IsPrime(2^n+19)]; // Vincenzo Librandi, Aug 28 2015

(PARI) for(n=1, 9e9, ispseudoprime(2^n+19)&&print1(n", ")) \\ M. F. Hasler, Jul 18 2016

CROSSREFS

Cf. A019434 (primes 2^n+1), A057732 (2^n+3), A059242 (2^n+5), A057195 (2^n+7), A057196(2^n+9), A102633 (2^n+11), A102634 (2^n+13), A057197 (2^n+15), A057200 (2^n+17), A057221 (this), A057201 (2^n+21), A057203 (2^n+23).

Sequence in context: A218940 A005432 A009422 * A180892 A196497 A127115

Adjacent sequences:  A057218 A057219 A057220 * A057222 A057223 A057224

KEYWORD

nonn,more

AUTHOR

Robert G. Wilson v, Sep 17 2000

EXTENSIONS

a(11)-a(13) from Robert Price, Aug 27 2015

Edited by M. F. Hasler, Jul 18 2016

STATUS

approved

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Last modified August 4 06:02 EDT 2021. Contains 346442 sequences. (Running on oeis4.)