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 A060787 #34 May 05 2025 01:37:45
%S A060787 0,18,108,270,504,810,1188,1638,2160,2754,3420,4158,4968,5850,6804,
%T A060787 7830,8928,10098,11340,12654,14040,15498,17028,18630,20304,22050,
%U A060787 23868,25758,27720,29754,31860,34038,36288,38610,41004,43470,46008,48618,51300,54054,56880,59778
%N A060787 a(n) = 18*(n - 2)*(2*n - 5).
%C A060787 Except for first term Engel expansion of cosh(1/3); cf. A006784 for Engel expansion definition. - _Benoit Cloitre_, Mar 03 2002
%D A060787 Luigi Berzolari, Allgemeine Theorie der Höheren Ebenen Algebraischen Kurven, Encyclopädie der Mathematischen Wissenschaften mit Einschluss ihrer Anwendungen. Band III_2. Heft 3, Leipzig: B. G. Teubner, 1906. p. 341.
%D A060787 Henri Brocard and Timoléon Lemoyne, Courbes géométriques remarquables (courbes spéciales) Planes et Gauches. Tome I, Paris: Albert Blanchard, 1967 [First publ. 1919]; see p. 135.
%H A060787 Harry J. Smith, <a href="/A060787/b060787.txt">Table of n, a(n) for n = 2..1000</a>
%H A060787 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A060787 G.f.: 18*x^3*(1 + 3*x)/(1 - x)^3. - _Colin Barker_, Feb 29 2012
%F A060787 From _Amiram Eldar_, May 05 2025: (Start)
%F A060787 Sum_{n>=3} 1/a(n) = log(2)/9.
%F A060787 Sum_{n>=3} (-1)^(n+1)/a(n) = Pi/36 - log(2)/18. (End)
%t A060787 a[n_] := 18*(n-2)*(2*n-5); Array[a, 50, 2] (* _Amiram Eldar_, May 05 2025 *)
%o A060787 (PARI) a(n) = 18*(n - 2)*(2*n - 5) \\ _Harry J. Smith_, Jul 11 2009
%Y A060787 Cf. A006784.
%K A060787 nonn,easy
%O A060787 2,2
%A A060787 Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), Apr 28 2001