OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
5^2=25 and 2+5=7 is prime.
MAPLE
P:=proc(k) if isprime(convert(convert(5^k, base, 10), `+`)) then k; fi; end: seq(P(n), n=1..200);
MATHEMATICA
a={}; For[n=1, n<200, n++, If[PrimeQ[Plus@@IntegerDigits[5^n]], AppendTo[a, n]]]; a (* Vincenzo Librandi, Apr 17 2013 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Oct 30 2007
EXTENSIONS
Corrected name and new Maple code by_Paolo P. Lava_, Jun 24 2024
STATUS
approved