

A252789


Numbers m such that 4^m + m is a semiprime.


1




OFFSET

1,1


LINKS

Table of n, a(n) for n=1..9.


EXAMPLE

7 is in this sequence because 4^7+7 = 37*443 and these two factors are prime.
19 is in this sequence because 4^19+19 = 11*24988900633 and these two factors are prime.


MATHEMATICA

Select[Range[130], PrimeOmega[4^# + #]==2 &]


PROG

(MAGMA) IsSemiprime:=func<i  &+[d[2]: d in Factorization(i)] eq 2>; [m: m in [1..130]  IsSemiprime(s) where s is 4^m+m];
(PARI) main(m)=select(m>bigomega(4^m + m)==2, vector(m, i, i)); \\ Anders HellstrÃ¶m, Aug 14 2015


CROSSREFS

Cf. similar sequences listed in A252788.
Cf. A252657.
Sequence in context: A051937 A119327 A152728 * A099061 A078163 A108766
Adjacent sequences: A252786 A252787 A252788 * A252790 A252791 A252792


KEYWORD

nonn,more


AUTHOR

Vincenzo Librandi, Dec 24 2014


EXTENSIONS

a(6)a(9) from Carl Schildkraut, Aug 14 2015


STATUS

approved



