OFFSET
1,2
COMMENTS
From Robert Israel, Mar 12 2023: (Start)
The number and its multiple must have the same number of digits.
Infinite families of terms include 10^n + 2, 10^n + 3, 10^n + 9, (4*10^n - 1)/3, 1.5*10^n + 9, (5*10^n - 1)/3, 2*10^n - 3, 2*10^n - 1, 2*10^n + 1, 2*10^n + 4, 2*10^n+8, 3*10^n - 5, 3*10^n - 4, 3*10^n - 2, 3*10^n + 1, (7*10^n - 1)/3, 4*10^n - 3, 4*10^n + 2, 5*10^n - 3, 5*10^n - 1. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..215
EXAMPLE
1997*3=5991, which differs in just one digit from 7991, the reverse of 1997.
MAPLE
filter:= proc(n) local L, d, m, Lp;
L:= ListTools:-Reverse(convert(n, base, 10));
d:= nops(L)-1;
for m from 2*n by n while ilog10(m) = d do
Lp:= convert(m, base, 10);
if nops(subs(0=NULL, L-Lp) = 1 then return true fi;
od;
false
end proc:
select(filter, [seq($ (10^d) .. (5*10^d-1), d=0..4)]); # Robert Israel, Mar 12 2023
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Erich Friedman, Jul 21 2001
EXTENSIONS
Offset changed by Robert Israel, Mar 12 2023
STATUS
approved