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proposed
approved
editing
proposed
Robert Israel, <a href="/A141322/b141322.txt">Table of n, a(n) for n = 1..10000</a>
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
approved
editing
_Jonathan Vos Post (jvospost3(AT)gmail.com), _, Aug 02 2008
Extended beyond 330 by _R. J. Mathar (mathar(AT)strw.leidenuniv.nl), _, Aug 09 2008
Nonpalindromes which are products of two palindromes in base 10.
10, 12, 14, 15, 16, 18, 20, 21, 24, 25, 27, 28, 30, 32, 35, 36, 40, 42, 45, 48, 49, 54, 56, 63, 64, 72, 81, 110, 132, 154, 165, 176, 198, 220, 231, 264, 275, 297, 302, 308, 322, 330, 342, 352, 362, 382, 385, 396, 423, 440, 453, 462, 483, 495, 504, 513, 524, 528
1,1
726 is in this sequence because 22 * 33 = 726, 22 and 33 are palindromes base 10, but 726 is not a palindrome base 10.
base,easy,nonn
Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 02 2008
Extended beyond 330 by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 09 2008
approved