OFFSET
1,1
COMMENTS
Trivially, if integer k is a term of this sequence, then R(k) is a term as well.
If n is in the sequence, then so is (10^m+1)*n where 10^m > n. In particular, the sequence is infinite. - Robert Israel, Aug 14 2014
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..500
EXAMPLE
The prime divisors of 87912 and R(87912) = 21978 are both {2, 3, 11, 37}, so 87912 and 21978 are both in the sequence.
MAPLE
revdigs:= proc(n)
local L, nL, i;
L:= convert(n, base, 10);
nL:= nops(L);
add(L[i]*10^(nL-i), i=1..nL);
end:
filter:= proc(n) local r;
r:= revdigs(n);
r <> n and numtheory:-factorset(r) = numtheory:-factorset(n)
end proc:
select(filter, [$10 .. 10^6]); # Robert Israel, Aug 14 2014
MATHEMATICA
r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[If[r[n] != n && Select[Divisors[n], PrimeQ] == Select[Divisors[r[n]], PrimeQ], Print[n]], {n, 1, 10^6}]
PROG
(Python)
from sympy import primefactors
A110819 = [n for n in range(1, 10**6) if str(n) != str(n)[::-1] and primefactors(n) == primefactors(int(str(n)[::-1]))] # Chai Wah Wu, Aug 14 2014
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Ryan Propper, Sep 15 2005
STATUS
approved