OFFSET
1,1
FORMULA
EXAMPLE
4, 6, and 9 are semiprimes with 1 digit. So a(1) = 3.
PROG
(PARI) vector(8, n, sum(k=10^(n-1), 10^n-1, bigomega(k)==2))
CROSSREFS
KEYWORD
nonn,hard,base
AUTHOR
Derek Orr, Aug 15 2014
EXTENSIONS
a(9)-a(18) from A066265, added by Jens Kruse Andersen, Aug 16 2014
a(19)-a(21) from A066265, added by Jon E. Schoenfield, Feb 10 2022
STATUS
approved