OFFSET
1,2
COMMENTS
Next terms: 347?, 479, 521, 551, .... - Charles R Greathouse IV, Aug 17 2015
FORMULA
1 is in this sequence because 8^1+1 = 3*3 is semiprime.
7 is in this sequence because 8^7+7 = 3*699053 and these two factors are prime.
MATHEMATICA
Select[Range[70], PrimeOmega[8^# + #]==2 &]
PROG
(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..70] | IsSemiprime(s) where s is 8^m+m];
(PARI) is(n)=bigomega(8^n+n)==2 \\ Charles R Greathouse IV, Aug 14 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Dec 25 2014
EXTENSIONS
a(9)-a(10) from Luke March, Jul 26 2015
a(11) from Carl Schildkraut, Aug 14 2015
a(12)-a(13) from Charles R Greathouse IV, Aug 17 2015
STATUS
approved