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A306980 Decimal expansion of the sum of the reciprocals of the star numbers (A003154). 1

%I #8 Mar 20 2019 04:36:30

%S 1,1,5,9,1,7,3,3,1,9,6,3,2,1,7,4,6,9,5,0,7,8,5,6,6,6,2,4,0,6,7,4,3,7,

%T 8,7,6,8,4,4,6,3,5,5,1,1,9,5,5,9,3,9,5,5,3,9,0,2,4,4,9,7,4,6,9,9,6,9,

%U 5,3,5,6,5,1,4,1,1,6,8,4,3,4,5,0,0,4,2

%N Decimal expansion of the sum of the reciprocals of the star numbers (A003154).

%F Equals Sum_{n>=1} 1/(6*n*(n-1) + 1) = x * tan(x) with x = Pi/(2*sqrt(3)).

%e 1.15917331963217469507856662406743787684463551195593...

%t s[n_]:=6*n*(n-1) + 1; RealDigits[Sum[1/s[n], {n,1,Infinity}], 10, 100][[1]]

%Y Cf. A003154, A093766 (Pi/(2*sqrt(3))).

%K nonn,cons

%O 1,3

%A _Amiram Eldar_, Mar 18 2019

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Last modified March 29 05:16 EDT 2024. Contains 371264 sequences. (Running on oeis4.)