OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..908
EXAMPLE
869=11*79 is semiprime and 968=2^3*11^2 is powerful.
MAPLE
N:= 99999:
S:= {1}:
p:= 1:
do
p:= nextprime(p);
if p^2 > N then break fi;
S:= S union map(t -> seq(t*p^j, j=2..floor(log[p](N/t))), S);
od:
digrev:= proc(x) local L;
L:= convert(x, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
sort(convert({10} union select(t -> numtheory:-bigomega(t)=2, map(digrev, select(t -> t mod 10 <> 0, S))), list)); # Robert Israel, Dec 03 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Jan 31 2006
STATUS
approved