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 A029987 #20 Feb 10 2025 19:56:58 %S A029987 0,1,25,289,441,4225,5041,6889,66049,74529,78961,100489,1050625, %T A029987 1113025,16785409,17313921,17581249,19368801,26594649,26822041, %U A029987 27258841,268468225,272613121,284428225,297183121,4295098369 %N A029987 Squares which are palindromes in base 4. %H A029987 Chai Wah Wu, <a href="/A029987/b029987.txt">Table of n, a(n) for n = 1..408</a> %H A029987 Patrick De Geest, <a href="https://www.worldofnumbers.com/nobase10pg2.htm">Palindromic Squares in bases 2 to 17</a> %e A029987 5^2 = 25 in base 4 is 121, which is a palindrome, hence 25 is in the sequence. %e A029987 6^2 = 36 in base 4 is 210, which is not a palindrome, so 36 is not in the sequence. %t A029987 palindromicQ[n_, b_:10] := TrueQ[IntegerDigits[n, b] == Reverse[IntegerDigits[n, b]]]; Select[Range[1000]^2, palindromicQ[#, 4] &] (* _Alonso del Arte_, Mar 04 2017 *) %t A029987 Select[Range[0,70000]^2,IntegerDigits[#,4]==Reverse[IntegerDigits[#,4]]&] (* _Harvey P. Dale_, May 07 2022 *) %o A029987 (PARI) lista(nn) = for (n=0, nn, d = digits(n^2, 4); if (Vecrev(d) == d, print1(n^2, ", "))); \\ _Michel Marcus_, Mar 05 2017 %Y A029987 Cf. A029986. %K A029987 nonn,base %O A029987 1,3 %A A029987 _Patrick De Geest_