OFFSET
1,2
COMMENTS
An element of this sequence is prime iff it has 2 digits, which is the case for a(2)=11 through a(22); sequence A096489 lists exactly these and the leading term a(1)=1 (the only noncomposite number which is not prime). - M. F. Hasler, Nov 29 2007
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
MAPLE
q:= n-> is(length(n)=numtheory[tau](n)):
select(q, [$1..1100])[]; # Alois P. Heinz, Jun 18 2021
MATHEMATICA
Select[Range[1100], IntegerLength[#]==DivisorSigma[0, #]&] (* Harvey P. Dale, Oct 19 2015 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Ray Chandler, Jun 28 2004
EXTENSIONS
Edited by M. F. Hasler, Nov 29 2007
STATUS
approved