1,1
Table of n, a(n) for n=1..5.
3121 = 5^5 - 4 is prime and therefore is in the sequence.
n:=1000: S:={}: for i from 1 to n do if type(5^i-4, prime)=true then S:=S union {5^i-4} end if od; S;
Select[5^Range[90]-4, PrimeQ] (* Harvey P. Dale, Aug 23 2013 *)
Cf. A059613, A135535, A228028.
Sequence in context: A183850 A002433 A107535 * A133526 A250523 A251061
Adjacent sequences: A181282 A181283 A181284 * A181286 A181287 A181288
nonn
Jonathan D. B. Hodgson, Oct 12 2010
approved
