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 A142599 #14 Sep 11 2022 10:09:26
%S A142599 5,2,77,35,221,20,437,143,725,56,1085,323,1517,110,2021,575,2597,182,
%T A142599 3245,899,3965,272,4757,1295,5621,380,6557,1763,7565,506,8645,2303,
%U A142599 9797,650,11021,2915,12317,812,13685,3599,15125,992,16637,4355,18221,1190,19877,5183,21605,1406,23405
%N A142599 Second trisection of A061037.
%C A142599 From Balmer spectrum of hydrogen. First trisection is A142590.
%H A142599 G. C. Greubel, <a href="/A142599/b142599.txt">Table of n, a(n) for n = 1..10000</a>
%H A142599 <a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,3,0,0,0,-3,0,0,0,1).
%F A142599 Sum_{n>=1} 1/a(n) = 5*Pi/(24*sqrt(3)) + 1/2. - _Amiram Eldar_, Sep 11 2022
%t A142599 A061037[n_] := Numerator[(n-2)*(n+2)/(4*n^2)]; Table[A061037[n], {n, 1, 300}][[3 ;; ;; 3]] (* _G. C. Greubel_, Sep 19 2018 *)
%Y A142599 Cf. A061037, A142590.
%K A142599 nonn,easy
%O A142599 1,1
%A A142599 _Paul Curtz_, Sep 23 2008
%E A142599 Edited by _N. J. A. Sloane_, Sep 27 2008
%E A142599 Terms a(18) onward added by _G. C. Greubel_, Sep 19 2018