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A141322 Nonpalindromes which are products of two palindromes in base 10.

%I A141322 #6 Jan 06 2020 20:35:02
%S A141322 10,12,14,15,16,18,20,21,24,25,27,28,30,32,35,36,40,42,45,48,49,54,56,
%T A141322 63,64,72,81,110,132,154,165,176,198,220,231,264,275,297,302,308,322,
%U A141322 330,342,352,362,382,385,396,423,440,453,462,483,495,504,513,524,528
%N A141322 Nonpalindromes which are products of two palindromes in base 10.
%H A141322 Robert Israel, <a href="/A141322/b141322.txt">Table of n, a(n) for n = 1..10000</a>
%F A141322 {A140332 INTERSECTION COMPLEMENT(A002113)} = {n in A115683 and n <> A004086(n)}.
%e A141322 726 is in this sequence because 22 * 33 = 726, 22 and 33 are palindromes base 10, but 726 is not a palindrome base 10.
%p A141322 digrev:= proc(n) local L,i; L:= convert(n,base,10); add(L[-i]*10^(i-1),i=1..nops(L)) end:
%p A141322 N:=3: # for terms of at most N digits
%p A141322 Res:= $0..9:
%p A141322 for d from 2 to N do
%p A141322   if d::even then
%p A141322     m:= d/2;
%p A141322     Res:= Res, seq(n*10^m + digrev(n), n=10^(m-1)..10^m-1);
%p A141322   else
%p A141322     m:= (d-1)/2;
%p A141322     Res:= Res, seq(seq(n*10^(m+1)+y*10^m+digrev(n), y=0..9), n=10^(m-1)..10^m-1);
%p A141322   fi
%p A141322 od:
%p A141322 Palis:= [Res]:
%p A141322 Res:= NULL:
%p A141322 for i from 3 to nops(Palis) while Palis[i]^2 <= 10^N do
%p A141322   for j from i to nops(Palis) while Palis[i]*Palis[j] <= 10^N do
%p A141322      v:= Palis[i]*Palis[j];      if digrev(v) <> v then Res:= Res, v fi;
%p A141322 od od:sort(convert({Res},list)); # _Robert Israel_, Jan 06 2020
%Y A141322 Cf. A002113, A004086, A140332.
%K A141322 base,easy,nonn
%O A141322 1,1
%A A141322 _Jonathan Vos Post_, Aug 02 2008
%E A141322 Extended beyond 330 by _R. J. Mathar_, Aug 09 2008