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A116999 Numbers k such that 2^k - prime(k)^2 is prime. 0
11, 15, 17, 23, 27, 47, 231, 457, 1249, 1529, 2343, 4693, 5939, 5997, 8367, 19855, 21295 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No more terms below 30000. - Giovanni Resta, Apr 03 2006

LINKS

Table of n, a(n) for n=1..17.

EXAMPLE

15 is in the sequence because the 15th prime is 47 and 2^15 - 47^2 = 30559 is prime.

MAPLE

a:=proc(n) if isprime(2^n-ithprime(n)^2) then n else fi end: seq(a(n), n=1..1600); # Emeric Deutsch, Apr 06 2006

MATHEMATICA

Select[Range[6000], PrimeQ[2^# - Prime[#]^2] &] (* Michael De Vlieger, Feb 02 2019 *)

PROG

(PARI) for(i=1, 2000, if(isprime(2^i-prime(i)^2), print1(i, ", ")))

CROSSREFS

Sequence in context: A186404 A111322 A069822 * A279422 A053675 A031944

Adjacent sequences:  A116996 A116997 A116998 * A117000 A117001 A117002

KEYWORD

hard,more,nonn

AUTHOR

Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 03 2006

EXTENSIONS

Corrected and extended by Giovanni Resta, Apr 03 2006

STATUS

approved

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Last modified March 25 16:26 EDT 2019. Contains 321470 sequences. (Running on oeis4.)