A374813 Decimal expansion of Sum_{k>=0} cos(2k*Pi/5)/2^k.
8, 9, 8, 5, 1, 9, 4, 1, 8, 2, 6, 6, 1, 1, 8, 8, 5, 6, 2, 7, 7, 8, 6, 3, 2, 4, 2, 0, 3, 5, 3, 8, 4, 3, 3, 3, 9, 7, 2, 9, 3, 3, 1, 4, 6, 4, 3, 2, 8, 1, 5, 7, 6, 0, 8, 5, 1, 8, 1, 7, 6, 0, 8, 6, 4, 8, 8, 9, 6, 1, 7, 3, 8, 2, 1, 1, 8, 4, 1, 0, 8, 0, 3, 6, 1, 8
Offset: 0
Examples
0.8985194182661188562778632420353843339729...
Crossrefs
Cf. A373021 (includes guide to related sequences).
Programs
-
Mathematica
{b, m, h} = {2, 5, 2}; s = Sum[Cos[ h k Pi/m]/b^k, {k, 0, Infinity}] d = N[s, 100] First[RealDigits[d], 100]
Formula
Equals (49 + 3*sqrt(5))/62.
Equals Sum_{k>=0} cos(8 k*Pi/5)/2^k.
Minimal polynomial: 19 - 49 x + 31 x^2.
Equals 2 - 2*A373017. - R. J. Mathar, Aug 27 2024