OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(5) = 117 is a term because 117 = 3^2 * 13 has 3 prime factors, counted with multiplicity, and so does its reversal 711 = 3^2 * 79.
MAPLE
rev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
select(t -> numtheory:-bigomega(t) = 3 and numtheory:-bigomega(rev(t))=3, [$1..10000]);
MATHEMATICA
Select[Range[710], PrimeOmega[#]==3&&PrimeOmega[FromDigits[Reverse[IntegerDigits[#]]]]==3&] (* Stefano Spezia, Nov 07 2023 *)
PROG
(Python)
from sympy import factorint
def tp(n): return sum(factorint(n).values()) == 3
def ok(n): return tp(n) and tp(int(str(n)[::-1]))
print([k for k in range(10**3) if ok(k)]) # Michael S. Branicky, Nov 21 2023
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov and Robert Israel, Nov 06 2023
STATUS
approved