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A118253 Decimal expansion of Product_{k>=1} sinc(2Pi/(2k+1)). 1
1, 8, 0, 5, 5, 0, 5, 4, 1, 8, 4, 9, 8, 5, 1, 9, 2, 3, 9, 1, 2, 3, 7, 2, 5, 9, 2, 9, 3, 0, 5, 0, 6, 0, 7, 5, 9, 1, 1, 3, 4, 0, 2, 3, 5, 8, 0, 5, 6, 1, 8, 3, 9, 5, 4, 1, 2, 3, 5, 9, 9, 9, 2, 2, 1, 7, 6, 6, 3, 1, 8, 4, 5, 9, 3, 0, 6, 2, 0, 7, 3, 5, 0, 6, 0, 6, 6, 2, 7, 3, 3, 1, 1, 0, 6, 8, 7, 6, 0, 2, 9, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..101.

Eric Weisstein's World of Mathematics, Sinc Function

FORMULA

Pi/(2K), where K is given by A051762.

EXAMPLE

0.180550541849851923912372592930506075911340235805618395412359992217663184593...

MAPLE

evalf(Pi/(2*(product(sec(Pi/k), k = 3..infinity))), 104); # Vaclav Kotesovec, Aug 16 2015

MATHEMATICA

digits = 102; $MaxExtraPrecision = 100; exactEnd = 100; seriesOrder = 60; f[n_] := Log[Sinc[2Pi/(2n + 1)]]; exactSum = Sum[f[n], {n, 1, exactEnd}]; se = Series[f[n], {n, Infinity, seriesOrder}] // Normal; extraSum = Sum[se, {n, exactEnd + 1, Infinity}]; RealDigits[Exp[exactSum + extraSum ], 10, digits] // First (* Jean-Fran├žois Alcover, Feb 07 2013 *)

CROSSREFS

Cf. A051762.

Sequence in context: A155528 A096152 A021558 * A135001 A146293 A019724

Adjacent sequences:  A118250 A118251 A118252 * A118254 A118255 A118256

KEYWORD

nonn,cons

AUTHOR

Eric W. Weisstein, Apr 18 2006

EXTENSIONS

Last digit corrected by Vaclav Kotesovec, Aug 16 2015

STATUS

approved

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Last modified April 20 14:27 EDT 2019. Contains 322310 sequences. (Running on oeis4.)