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 A273229 #9 May 21 2016 22:42:13
%S A273229 1,36,400,3136,24336,115600,118336,126736,211600,309136,430336,577600,
%T A273229 5973136,19713600,30869136,53582400,3086469136,4310710336,71526293136,
%U A273229 111155560000,112104432400,113531259136,137756776336,206170483600,245996160400,262303768336,308642469136
%N A273229 Squares that remain squares if you decrease them by a repunit with the same number of digits.
%C A273229 Apart from the initial term, any number ends in 0 or 6.
%H A273229 Giovanni Resta, <a href="/A273229/b273229.txt">Table of n, a(n) for n = 1..10000</a>
%e A273229 1 - 1 = 0 = 0^2;
%e A273229 36 - 11 = 25 = 5^2;
%e A273229 400 - 111 = 289 = 17^2;
%p A273229 P:=proc(q,h) local n; for n from 1 to q do
%p A273229 if type(sqrt(n^2-h*(10^(ilog10(n^2)+1)-1)/9),integer) then print(n^2);
%p A273229 fi; od; end: P(10^9,1);
%t A273229 sol[k_] := Block[{x, e = IntegerLength@k, d = Divisors@k}, Union[#+k/# & /@ Select[ Take[d, Ceiling[ Length@d/2]], EvenQ[ x= #+k/#] && IntegerLength[ x^2/4] == e &]]^2/4]; r[n_] := (10^n-1)/9; Flatten[sol /@ r /@ Range[12]] (* _Giovanni Resta_, May 18 2016 *)
%Y A273229 Cf. A002275, A061844, A273230-A273234.
%K A273229 nonn,easy,base
%O A273229 1,2
%A A273229 _Paolo P. Lava_, May 18 2016