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 A155137 #7 Oct 18 2022 15:08:01
%S A155137 0,27,48,57,48,15,0,48,147,288,477,720,1023,1392,1833,2352,2955,3648,
%T A155137 4437,5328,6327,7440,8673,10032,11523,13152,14925,16848,18927,21168,
%U A155137 23577,26160,28923,31872,35013,38352,41895,45648,49617,53808,58227
%N A155137 a(n) = nonnegative value y such that (A155135(n), y) is a solution to the Diophantine equation x^3+28*x^2 = y^2.
%C A155137 Agrees with A155138 except for insertion of zero after a(6) = 15.
%H A155137 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F A155137 G.f.: 3*x*(9-20*x+9*x^2+16*x^5+x^6-19*x^7+x^8+5*x^9)/(1-x)^4.
%e A155137 (A155135(3), a(3)) = (-24, 48) is a solution: (-24)^3+28*(-24)^2 = -13824+16128 = 2304 = 48^2.
%e A155137 (A155135(7), a(8)) = (0, 0) is a solution: 0^3+28*0^2 = 0 = 0^2.
%e A155137 (A155135(8), a(8)) = (8, 48) is a solution: 8^3+28*8^2 = 512+1792 = 2304 = 48^2.
%t A155137 CoefficientList[Series[3x (9-20x+9x^2+16x^5+x^6-19x^7+x^8+5x^9)/(1-x)^4,{x,0,40}],x] (* or *) LinearRecurrence[{4,-6,4,-1},{0,27,48,57,48,15,0,48,147,288,477},50] (* _Harvey P. Dale_, Sep 02 2021 *)
%o A155137 (Magma) [ Integers()!SquareRoot(a) : n in [ -30..1500] | IsSquare(a) where a is n^3+28*n^2 ];
%o A155137 (PARI) a(n)=if(n>6, n^3 - 3*n^2 - 25*n + 27, [0, 27, 48, 57, 48, 15, 0][n+1]) \\ _Charles R Greathouse IV_, Oct 18 2022
%Y A155137 Cf. A155135, A155138, A153642.
%K A155137 nonn,easy
%O A155137 1,2
%A A155137 _Klaus Brockhaus_, Jan 21 2009