OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
262 = 2 * 131.
264 = 6 * 11.
275 = 5 * 55.
MAPLE
revdigs:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
N:=4; # to get terms <= 2*10^N
Pals:= $2..9:
for d from 2 to N do
if d::even then
m:= d/2;
Pals:= Pals, seq(n*10^m + revdigs(n), n=10^(m-1)..10^m-1);
else
m:= (d-1)/2;
Pals:= Pals, seq(seq(n*10^(m+1)+y*10^m+revdigs(n), y=0..9), n=10^(m-1)..10^m-1);
fi
od:
Pals:= {Pals}: nP:= nops(Pals):
P2:= select(`<`, {seq(seq(Pals[i]*Pals[j], j=1..i), i=1..nP)}, 2*10^N):
sort(convert(P2, list)); # Robert Israel, Mar 16 2020
MATHEMATICA
pal = Select[ Range[2, 400], # == FromDigits@ Reverse@ IntegerDigits@ # &]; Select[Union[Times @@@ Tuples[pal, 2]], # <= 400 &] (* Giovanni Resta, Jun 20 2016 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Jan 31 2006
STATUS
approved