OFFSET
1,2
COMMENTS
a(10) >= 868. - Hugo Pfoertner, Jul 28 2019
EXAMPLE
2 is OK because 5^2 + 2^5 = 25 + 32 = 57 = 3*19 (semiprime).
MATHEMATICA
Select[Range[100], PrimeOmega[5^# + #^5]==2&] (* Vincenzo Librandi, May 21 2014 *)
PROG
(Magma)IsSemiprime:=func< n|&+[k[2]: k in Factorization(n)] eq 2 >; [n: n in [1..85]|IsSemiprime(5^n+n^5)]; // Vincenzo Librandi, Dec 16 2010
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Zak Seidov, Feb 22 2006
EXTENSIONS
a(8), a(9) from Hugo Pfoertner, Jul 28 2019
STATUS
approved