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A306980 Decimal expansion of the sum of the reciprocals of the star numbers (A003154). 1
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, 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, 5, 3, 5, 6, 5, 1, 4, 1, 1, 6, 8, 4, 3, 4, 5, 0, 0, 4, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..87.

FORMULA

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

EXAMPLE

1.15917331963217469507856662406743787684463551195593...

MATHEMATICA

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

CROSSREFS

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

Sequence in context: A010490 A021173 A266553 * A063921 A227574 A214869

Adjacent sequences:  A306977 A306978 A306979 * A306981 A306982 A306983

KEYWORD

nonn,cons

AUTHOR

Amiram Eldar, Mar 18 2019

STATUS

approved

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Last modified November 14 17:24 EST 2019. Contains 329126 sequences. (Running on oeis4.)