A019695 -id:A019695 - cp's OEIS frontend

A175618 Decimal expansion of product_{n>=2} (1-n^(-7)).

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

Offset: 0

R. J. Mathar, Jul 26 2010

			0.99165495...

E. Weisstein, Infinite Product, Mathworld.

Cf. A109219, A175615, A144666.

N[1/(7*Product[ Gamma[(-1)^(8*k/7 + 1)], {k, 1, 6}]), 105] // Re // RealDigits // First (* Jean-François Alcover, Feb 05 2013 *)

exp(suminf(j=1, (1 - zeta(7*j))/j)) \\ Vaclav Kotesovec, Dec 15 2020

Equals 1/product_{t=1..6} Gamma(2-exp(2*Pi*i*t/7)), where i is the imaginary unit and 2*Pi/7 = A019695.

Equals exp(Sum_{j>=1} (1 - zeta(7*j))/j). - Vaclav Kotesovec, Dec 15 2020

A216606 Decimal expansion of 360/7.

Original entry on oeis.org

5, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7, 1, 4, 2, 8, 5, 7

Offset: 2

Paul Curtz, Sep 10 2012

A020806 preceded by a 5.

Number of degrees in the exterior angle of an equilateral heptagon. Since 1969, used in many (orbiform or Reuleaux) heptagonal coins. Zambia has a natural heptagonal coin. Brazil and Costa Rica have a coin with the natural heptagon inscribed in the coin's disk.

			51.42857...

World of Coins, An Alphabet of Heptagons: Seven-sided Coins.
Index entries for linear recurrences with constant coefficients, signature (1,0,-1,1).

Cf. A019695, A020806, A021018, A060708, A068028, A178817, A178818.

Digits:=100: evalf(360/7); # Wesley Ivan Hurt, Jun 28 2016

Flatten[RealDigits[360/7, 10, 100]] (* Wesley Ivan Hurt, Jun 28 2016 *)

360/7. \\ Charles R Greathouse IV, Sep 12 2012

a(n) = 50 + 10*A020806(n).
After 5, of period 6: repeat [1, 4, 2, 8, 5, 7].
From Wesley Ivan Hurt, Jun 28 2016: (Start)
G.f.: x^3*(5-4*x+3*x^2+3*x^3+2*x^4) / (1-x+x^3-x^4).
a(n) = 9/2 + 11*cos(n*Pi)/6 + 5*cos(n*Pi/3)/3 + sqrt(3)*sin(n*Pi/3), n>2.
a(n) = a(n-1) - a(n-3) + a(n-4) for n>6, a(n) = a(n-6) for n>8. (End)

cp's OEIS Frontend

A175618 Decimal expansion of product_{n>=2} (1-n^(-7)).

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