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 A214391 #12 May 27 2025 11:11:44
%S A214391 3,21,168,280,210,1365,42315,8463,45136,406224,253890,310310,744744,
%T A214391 744744,94582488,661416,110236,21496020,924328860,7394630880,
%U A214391 894750336480,5070251906720,5704033395060,6375096147420,6375096147420,2550038458968,2550038458968
%N A214391 Denominators of Sum_{n>=1} 1/A045542(n).
%C A214391 Goldbach-Euler: sum A214390(n)/a(n) -> 1, n -> oo.
%H A214391 Reinhard Zumkeller, <a href="/A214391/b214391.txt">Table of n, a(n) for n = 1..1000</a>
%H A214391 L. Bibiloni, P. Viader, and J. Paradis, <a href="https://web.archive.org/web/20240329125701/https://www.maa.org/sites/default/files/pdf/upload_library/22/Ford/bibiloni206.pdf">On a Series of Goldbach and Euler</a>, Amer. Math. Monthly, 113 (2006), pp. 206-220.
%o A214391 (Haskell)
%o A214391 import Data.Ratio ((%), denominator)
%o A214391 a214391 n = a214391_list !! (n-1)
%o A214391 a214391_list = map denominator $ scanl1 (+) $ map (1 %) a045542_list
%Y A214391 Cf. A214390 (numerators).
%K A214391 nonn,frac
%O A214391 1,1
%A A214391 _Reinhard Zumkeller_, Jul 15 2012