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 A027572 #21 Jan 19 2025 18:04:27 %S A027572 1,5,181,313,545,1690961,3162613,3187813,5258525,5824285,58281418285, %T A027572 1635446445361,3166046406613,124852060258421,149988757889941, %U A027572 310433303334013,582818040818285,12951570707515921,5227371841481737225,5649436330336349465,5816694029204966185 %N A027572 Palindromes of form n^2 + (n+1)^2. %C A027572 a(50) > 10^40. - _Patrick De Geest_, May 25 2021 %H A027572 Patrick De Geest, <a href="/A027572/b027572.txt">Table of n, a(n) for n = 1..49</a> %H A027572 Patrick De Geest, <a href="http://www.worldofnumbers.com/sumsquare.htm">Palindromic Sums of Squares of Consecutive Integers</a> %H A027572 Patrick De Geest, <a href="http://www.worldofnumbers.com/centered.htm">Palindromic Centered Polygonal Numbers</a> %F A027572 a(n) = (4*m^2 - 4*m + 2)/2 = (m-1)^2 + m^2 or a(n) = (4*n^2 + 4*n + 2)/2 = n^2 + (n+1)^2 with n = m - 1. %t A027572 Select[Total/@Partition[Range[0,2000]^2,2,1],PalindromeQ] (* The program generates the first 10 terms of the sequence. *) (* _Harvey P. Dale_, Jan 19 2025 *) %Y A027572 Cf. A001844, A027571, A050236, A050239. %Y A027572 A050239 is a subsequence. %K A027572 nonn,base %O A027572 1,2 %A A027572 _Patrick De Geest_ %E A027572 a(18)-a(21) from _Donovan Johnson_, Aug 26 2012 %E A027572 a(1)=1 added by _Philip Mizzi_, Sep 02 2019 %E A027572 a(22)-a(49) from _Patrick De Geest_, May 25 2021