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A369500 Decimal expansion of Sum_{k=-oo..oo} 1/(2^(k/2)+2^(-k/2)). 0
4, 5, 3, 2, 3, 6, 0, 1, 4, 1, 8, 3, 4, 9, 6, 8, 7, 0, 2, 1, 4, 2, 4, 6, 8, 9, 8, 7, 9, 2, 8, 9, 6, 4, 7, 3, 7, 8, 6, 9, 7, 3, 8, 6, 7, 7, 3, 7, 9, 1, 1, 8, 4, 2, 4, 8, 0, 2, 7, 3, 0, 0, 3, 2, 0, 5, 5, 5, 0, 3, 6, 4, 8, 8, 3, 6, 7, 1, 5, 3, 5, 8, 2, 6, 2, 5, 4, 2, 0, 3, 0, 9, 1, 2, 6, 2, 6, 0, 6, 2, 1, 6, 5, 1, 7 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Larger than Pi/log(2) by less than 10^(-11).
LINKS
Gérard Maze and Lorenz Minder, A new family of almost identities, Elemente der Mathematik, Vol. 62, No. 3 (2007), pp. 89-97.
FORMULA
Equals (Pi/log(2)) * (1 + 2 * Sum_{k>=1} sech(2*k*Pi^2/log(2))).
EXAMPLE
4.5323601418349687021424689879289647378697386773791184248...
MATHEMATICA
RealDigits[Chop[N[Sum[1/(2^(k/2) + 2^(-k/2)), {k, -Infinity, Infinity}], 120]]][[1]]
PROG
(PARI) (Pi/log(2)) * (1 + 2 * sumpos(k = 1, 1/cosh(2*k*Pi^2/log(2))))
CROSSREFS
Cf. A163973.
Sequence in context: A114263 A094850 A163973 * A124118 A016716 A004485
KEYWORD
nonn,cons
AUTHOR
Amiram Eldar, Jan 25 2024
STATUS
approved

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Last modified June 20 17:22 EDT 2024. Contains 373530 sequences. (Running on oeis4.)