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Second trisection of A061037.
1

%I #14 Sep 11 2022 10:09:26

%S 5,2,77,35,221,20,437,143,725,56,1085,323,1517,110,2021,575,2597,182,

%T 3245,899,3965,272,4757,1295,5621,380,6557,1763,7565,506,8645,2303,

%U 9797,650,11021,2915,12317,812,13685,3599,15125,992,16637,4355,18221,1190,19877,5183,21605,1406,23405

%N Second trisection of A061037.

%C From Balmer spectrum of hydrogen. First trisection is A142590.

%H G. C. Greubel, <a href="/A142599/b142599.txt">Table of n, a(n) for n = 1..10000</a>

%H <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 Sum_{n>=1} 1/a(n) = 5*Pi/(24*sqrt(3)) + 1/2. - _Amiram Eldar_, Sep 11 2022

%t 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 Cf. A061037, A142590.

%K nonn,easy

%O 1,1

%A _Paul Curtz_, Sep 23 2008

%E Edited by _N. J. A. Sloane_, Sep 27 2008

%E Terms a(18) onward added by _G. C. Greubel_, Sep 19 2018