OFFSET
1,1
COMMENTS
This includes repunit semiprimes also.
Intersection of A001358 (semiprimes) and A007088 (numbers written in base 2). - Michel Marcus, Jan 27 2015
LINKS
Zak Seidov, Table of n, a(n) for n = 1..531
EXAMPLE
a(3)=1011 is a term because 1011 is a semiprime and contain digits 0 and 1 only.
MAPLE
N:= 12: # to get all terms with at most N digits
cands[1]:= {1}:
for d from 2 to N do
cands[d]:= map(t -> (10*t, 10*t+1), cands[d-1])
od:
select(numtheory:-bigomega = 2, `union`(seq(cands[d], d=1..N)));
# if using Maple 11 or lower, uncomment the next line
# sort(convert(%, list)); # Robert Israel, Jan 27 2015
PROG
(PARI) isok(n) = (bigomega(n)==2) && (vecmax(digits(n)) <= 1); \\ Michel Marcus, Jan 27 2015
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Shyam Sunder Gupta, Apr 29 2005
EXTENSIONS
Data corrected by Zak Seidov, Jan 27 2015
STATUS
approved