cp's OEIS Frontend

A048343 Total number of distinct palindromes of form 'n-digit number' x 'n-digit number_reversed' (n-digit number not palindromic).

%I A048343 #23 May 22 2025 10:21:34
%S A048343 0,1,3,10,19,44,86,171,308,551,920
%N A048343 Total number of distinct palindromes of form 'n-digit number' x 'n-digit number_reversed' (n-digit number not palindromic).
%H A048343 P. De Geest, <a href="https://www.worldofnumbers.com/reversal.htm">Palindromic Products of Non Palindromic Integers and their Reversals </a>
%e A048343 E.g., 3 solutions for 3-digit numbers: 102 * 201 = 20502; 112 * 211 = 23632; 122 * 221 = 26962.
%o A048343 (Python)
%o A048343 def A048343(n):
%o A048343     y, plist = 0, []
%o A048343     for i in range(10**(n-1),10**n):
%o A048343         s1 = str(i)
%o A048343         s2 = s1[::-1]
%o A048343         if s1 != s2:
%o A048343             p = i*int(s2)
%o A048343             if not p in plist:
%o A048343                 sp = str(p)
%o A048343                 if sp == sp[::-1]:
%o A048343                     plist.append(p)
%o A048343                     y += 1
%o A048343     return y # _Chai Wah Wu_, Sep 05 2014
%Y A048343 Cf. A048344.
%K A048343 nonn,base,more
%O A048343 1,3
%A A048343 _Patrick De Geest_, Feb 15 1999
%E A048343 More terms from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 18 2006
%E A048343 Offset changed and two terms added by _Lars Blomberg_, Nov 25 2011