OFFSET
1,1
COMMENTS
a(40) > 5*10^5. - Robert Price, Oct 15 2015
Since each term is even (n = 2*k), prime numbers of the form 2^k + 25 (see A104072) also have the form 4^k + 25. Those values of k are given in A204388. - Timothy L. Tiffin, Aug 06 2016
LINKS
Henri Lifchitz and Renaud Lifchitz, Search for 2^n+25, PRP Top Records.
FORMULA
a(n) = 2*A204388(n). - Timothy L. Tiffin, Aug 09 2016
EXAMPLE
For k = 2, 2^2 + 25 = 29.
For k = 4, 2^4 + 25 = 41.
For k = 6, 2^6 + 25 = 89.
MATHEMATICA
Delete[Union[Table[If[PrimeQ[2^n + 25], n, 0], {n, 1, 1000}]], 1]
Select[Range[0, 10000], PrimeQ[2^# + 25] &] (* Vincenzo Librandi, Aug 07 2016 *)
PROG
(Magma) [n: n in [1..1000] | IsPrime(2^n+25)]; // Vincenzo Librandi, Aug 07 2016
(PARI) is(n)=ispseudoprime(2^n+5^2) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
Cf. A019434 (primes 2^k+1), A057732 (2^k+3), A059242 (2^k+5), A057195 (2^k+7), A057196 (2^k+9), A102633 (2^k+11), A102634 (2^k+13), A057197 (2^k+15), A057200 (2^k+17), A057221 (2^k+19), A057201 (2^k+21), A057203 (2^k+23), this sequence (2^k+25), A157007 (2^k+27), A156982 (2^k+29), A247952 (2^k+31), A247953 (2^k+33), A220077 (2^k+35).
KEYWORD
nonn
AUTHOR
Edwin Dyke (ed.dyke(AT)btinternet.com), Feb 20 2009
EXTENSIONS
Extended by Vladimir Joseph Stephan Orlovsky, Feb 27 2011
a(29)-a(39) from Robert Price, Oct 15 2015
a(40)-a(48) found by Stefano Morozzi, added by Elmo R. Oliveira, Nov 25 2023
STATUS
approved