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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, 36583
OFFSET
1,1
COMMENTS
No more terms below 30000. - Giovanni Resta, Apr 03 2006
No more terms below 130000. - Michael S. Branicky, Jul 13 2024
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 * A309362 A279422 A333488
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
a(18) from Michael S. Branicky, Jun 23 2023
STATUS
approved