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 A028556 #12 Apr 29 2025 18:19:27
%S A028556 0,5,77,252,525,1221,2112,21312,56165,73437,276672,1265621,2114112,
%T A028556 2509052,29311392,69555596,71588517,122434221,126000621,540888045,
%U A028556 5401221045,21183638112,69069096096,71149694117,79158385197,2752360632572,7320655560237,12278611687221
%N A028556 Palindromes of form k*(k+4).
%H A028556 Michael S. Branicky, <a href="/A028556/b028556.txt">Table of n, a(n) for n = 1..49</a>
%H A028556 P. De Geest, <a href="https://www.worldofnumbers.com/consemor.htm">Palindromic Quasipronics of the form n(n+x)</a>
%F A028556 a(n) = A028555(n) * (A028555(n) + 4). - _Michael S. Branicky_, Jan 26 2022
%t A028556 Select[Table[k(k+4),{k,0,3510000}],PalindromeQ] (* _Harvey P. Dale_, Apr 29 2025 *)
%o A028556 (Python)
%o A028556 from itertools import count, islice
%o A028556 def ispal(n): s = str(n); return s == s[::-1]
%o A028556 def agen():
%o A028556 for k in count(0):
%o A028556 if ispal(k*(k+4)):
%o A028556 yield k*(k+4)
%o A028556 print(list(islice(agen(), 32))) # _Michael S. Branicky_, Jan 26 2022
%Y A028556 Cf. A028347, A028555.
%K A028556 nonn,base
%O A028556 1,2
%A A028556 _Patrick De Geest_
%E A028556 a(26) and beyond from _Michael S. Branicky_, Jan 26 2022