A252794 Numbers m such that 9^m + m is a semiprime.

1, 5, 68, 85, 86, 92, 136

Offset

1,2

Comments

a(8) > 435. - Carl Schildkraut, Aug 14 2015

Links

Table of n, a(n) for n=1..7.

Example

1 is in this sequence because 9^1+1 = 2*5 is semiprime.
5 is in this sequence because 9^5+5 = 2*29527 and these two factors are prime.

Mathematica

Select[Range[435], PrimeOmega[9^# + #]==2 &]

Prog

(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..435] | IsSemiprime(s) where s is 9^m+m];

Crossrefs

Cf. similar sequences listed in A252788.

Cf. A252662.

Sequence in context: A207979 A129963 A115764 * A328359 A003361 A363401

Adjacent sequences: A252791 A252792 A252793 * A252795 A252796 A252797

Keyword

nonn,more

Author

Vincenzo Librandi, Dec 27 2014

Extensions

a(4)-a(7) from Carl Schildkraut, Aug 14 2015

Status

approved