OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 39 is a term because 39 = 3*13 is a semiprime, its reversal 93 = 3*31 is a semiprime, and 93 > 39.
MAPLE
rev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
filter:= proc(n) local r;
r:= rev(n);
r > n and numtheory:-bigomega(n) = 2 and numtheory:-bigomega(r) = 2
end proc:
select(filter, [$1..2000]);
MATHEMATICA
s = {}; Do[fd = FromDigits[Reverse[IntegerDigits[k]]]; If[{2, 2} ==PrimeOmega[{fd, k}] && fd > k, AppendTo[s, k]], {k, 1000}]; s
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov and Robert Israel, Jun 17 2024
STATUS
approved