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A261579
Numbers m such that (4^m + 23) / 3 is prime.
1
2, 3, 5, 6, 27, 47, 66, 77, 83, 105, 197, 231, 293, 702, 1692, 3021, 6270, 6897, 7733, 14537, 15797, 21083, 21276, 28817, 65430, 111231, 137405, 141017, 185225
OFFSET
1,1
COMMENTS
a(30) > 450,000. - Robert Price, Oct 04 2018
EXAMPLE
2 is in the sequence because (4^2 + 23)/3 = 13 is prime.
3 is in the sequence because (4^3 + 23)/3 = 29 is prime.
MATHEMATICA
Select[Range[0, 5000], PrimeQ[(4^# + 23)/3] &]
PROG
(Magma) [n: n in [0..1500] | IsPrime((4^n+23) div 3)];
CROSSREFS
Cf. similar sequences listed in A261539.
Sequence in context: A263650 A345709 A076384 * A376655 A270517 A124648
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Aug 27 2015
EXTENSIONS
a(17)-a(28) from Robert Price, Feb 01 2017
a(29) from Robert Price, Oct 04 2018
STATUS
approved