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

1,1

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)

Links

Table of n, a(n) for n=1..14.

FactorDB, Status of 6^335+335

Example

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.

Mathematica

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

Prog

(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..90] | IsSemiprime(s) where s is 6^m+m];

Crossrefs

Cf. similar sequences listed in A252788.

Cf. A252659.

Sequence in context: A288371 A158217 A030284 * A068148 A036344 A165802

Adjacent sequences: A252788 A252789 A252790 * A252792 A252793 A252794

Keyword

nonn,more

Author

Vincenzo Librandi, Dec 25 2014

Extensions

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

Status

approved