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 A028337 #28 Apr 09 2025 15:12:28 %S A028337 2,6,272,6006,289982,2629262,6039306,27999972,28233282,2704884072, %T A028337 20278187202,20591819502,2592587852952,2936231326392,21809166190812, %U A028337 27237788773272,229145919541922,233552101255332,250087292780052,2243922442293422,2570769009670752,20333113431133302,27785925652958772 %N A028337 Palindromes of the form n(n+1). %H A028337 Patrick De Geest, <a href="https://www.worldofnumbers.com/consec.htm">Palindromic pronic numbers of the form n(n+1)</a> %H A028337 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PalindromicNumber.html">Palindromic Number.</a> %H A028337 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PronicNumber.html">Pronic Number.</a> %e A028337 272 belongs to the sequence as 272 = 16*17 is a palindrome. %t A028337 Select[2*Accumulate[Range[15820000]],IntegerDigits[#] == Reverse[ IntegerDigits[#]]&] (* _Harvey P. Dale_, Sep 03 2013 *) %o A028337 (Python) %o A028337 A028337_list, n = [], 0 %o A028337 for i in range(2,10**6,2): %o A028337 n += i %o A028337 s = str(n) %o A028337 if s == s[::-1]: %o A028337 A028337_list.append(n) # _Chai Wah Wu_, Jan 15 2015 %Y A028337 Cf. A028336. %K A028337 nonn,base %O A028337 1,1 %A A028337 _Patrick De Geest_ %E A028337 a(20)-a(23) from _G. C. Greubel_, Nov 04 2017