OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
726 is in this sequence because 22 * 33 = 726, 22 and 33 are palindromes base 10, but 726 is not a palindrome base 10.
MAPLE
digrev:= proc(n) local L, i; L:= convert(n, base, 10); add(L[-i]*10^(i-1), i=1..nops(L)) end:
N:=3: # for terms of at most N digits
Res:= $0..9:
for d from 2 to N do
if d::even then
m:= d/2;
Res:= Res, seq(n*10^m + digrev(n), n=10^(m-1)..10^m-1);
else
m:= (d-1)/2;
Res:= Res, seq(seq(n*10^(m+1)+y*10^m+digrev(n), y=0..9), n=10^(m-1)..10^m-1);
fi
od:
Palis:= [Res]:
Res:= NULL:
for i from 3 to nops(Palis) while Palis[i]^2 <= 10^N do
for j from i to nops(Palis) while Palis[i]*Palis[j] <= 10^N do
v:= Palis[i]*Palis[j]; if digrev(v) <> v then Res:= Res, v fi;
od od:sort(convert({Res}, list)); # Robert Israel, Jan 06 2020
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Aug 02 2008
EXTENSIONS
Extended beyond 330 by R. J. Mathar, Aug 09 2008
STATUS
approved