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 A273358 #15 Sep 08 2022 08:46:16 %S A273358 6,24,61,136,249,364,481,600,721,844,969,1329,1684,2041,2400,2761, %T A273358 3124,3489,3856,4225,4596,4969,5344,5721,6100,6481,6864,7249,7636, %U A273358 8025,8416,8809,9204,9601,10249,11364,12481,13600,14721,15844,16969,18096 %N A273358 Numbers n such that the decimal number concat(3,n) is a square. %C A273358 Elements are squares of integers in (sqrt(31), sqrt(40)) * sqrt(10)^k without the leading 3 elements for nonnegative k. - _David A. Corneth_, May 20 2016 %H A273358 Nathan Fox, <a href="/A273358/b273358.txt">Table of n, a(n) for n = 1..11067</a> %e A273358 61 is a member because 361 = 19^2 is a square. %e A273358 0 is not a member because 30 is not a square. %p A273358 t1:=[]; %p A273358 for k from 1 to 20000 do %p A273358 if issqr(k+3*10^length(k)) then t1:=[op(t1), k]; fi; %p A273358 od; %p A273358 t1; %o A273358 (Magma) [n: n in [1..20000 ] | IsSquare(Seqint(Intseq(n) cat Intseq(3)))]; // _Marius A. Burtea_, Mar 21 2019 %Y A273358 Cf. A272671, A273357, A273359, A273360, A273361, A273362, A273363, A273364. %K A273358 nonn,base %O A273358 1,1 %A A273358 _Nathan Fox_, _Brooke Logan_, and _N. J. A. Sloane_, May 20 2016