A252791 Numbers m such that 6^m + m is a semiprime.

2, 3, 5, 7, 11, 23, 41, 55, 73, 91, 131, 199, 221, 287

Offset: 1

Author

Vincenzo Librandi, Dec 25 2014

Keywords

• nonn
• more

Comments

From Kevin P. Thompson, May 01 2022: (Start)

a(15) >= 335.

391, 443, 607, 683, 737, and 745 are also terms in this sequence. (End)

Examples

			2 is in this sequence because 6^2+2 = 2*19 is semiprime.
7 is in this sequence because 6^7+7 = 271*1033 and these two factors are prime.
		

Links

• FactorDB, Status of 6^335+335

Crossrefs

Cf. similar sequences listed in A252788.

Cf. A252659.

Programs

Magma

IsSemiprime:=func; [m: m in [1..90] | IsSemiprime(s) where s is 6^m+m];

Mathematica

Select[Range[90], PrimeOmega[6^# + #]==2 &]

Extensions

a(10)-a(14) by Luke March, Jul 08 2015