This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A129623 #22 Sep 30 2024 16:24:59
%S A129623 252,403,574,736,765,976,1008,1207,1300,1458,1462,1612,1729,1855,1944,
%T A129623 2268,2296,2430,2668,2701,2944,3154,3478,3627,3640,4032,4275,4606,
%U A129623 4930,5092,5605,5848,6624,6786,7663,8722,20502,23632,26962,30492,31003,34222
%N A129623 Numbers which are the product of a non-palindrome and its reversal, where leading zeros are not allowed.
%C A129623 The smallest square in this sequence is 63504 = 252*252 = 144*441.
%H A129623 Michael S. Branicky, <a href="/A129623/b129623.txt">Table of n, a(n) for n = 1..11195</a> (terms < 10^9)
%e A129623 252 = 12*21.
%t A129623 Take[Union[ Transpose[ Select[Table[{n, n* FromDigits[Reverse[IntegerDigits[n]]]}, {n, 1000}], Mod[ #[[1]], 10] != 0 && #[[1]] != FromDigits[Reverse[IntegerDigits[ #[[1]]]]] &]][[2]]], 100]
%t A129623 upto2ndigits@n_ := Union@(If[(i = IntegerReverse@#) > #, i*#, Nothing] & /@Range@(10^n - 1)); upto2ndigits@3 (* _Hans Rudolf Widmer_, Sep 06 2024 *)
%o A129623 (Python)
%o A129623 from sympy import divisors
%o A129623 def ok(n): return any(n==d*int(s[::-1]) for d in divisors(n)[1:-1] if (s:=str(d))!=s[::-1] and s[-1]!="0")
%o A129623 print([k for k in range(36000) if ok(k)]) # _Michael S. Branicky_, Sep 07 2024
%o A129623 (Python) # instantly generates 44185 terms with n = 5
%o A129623 def aupto2ndigits(n): return(sorted(set(i*int(s[::-1]) for i in range(12, 10**n) if i%10 != 0 and (s:=str(i)) != s[::-1])))
%o A129623 print(aupto2ndigits(2))
%o A129623 # _Michael S. Branicky_, Sep 08 2024 after _Hans Rudolf Widmer_
%Y A129623 Cf. A072443, A076750.
%K A129623 base,nonn
%O A129623 1,1
%A A129623 _Tanya Khovanova_, May 30 2007
%E A129623 Offset corrected by _Stefano Spezia_, Sep 07 2024