|
|
A252661
|
|
Numbers m such that 8^m - m is a semiprime.
|
|
2
|
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
EXAMPLE
|
2 is in this sequence because 8^2-2 = 2*31 is semiprime.
9 is in this sequence because 8^9-9 = 23*5835553 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];
|
|
CROSSREFS
|
Cf. similar sequences listed in A252656.
|
|
KEYWORD
|
nonn,more,hard
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|