A387448 Decimal expansion of cos(Pi/28).

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

Offset

0,1

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

R. J. Mathar, Reduction formulas of the cosine of integer fractions of pi, (2008) vixra:2210.0026.

Index entries for algebraic numbers, degree 12

Formula

Equals sin(13*Pi/28) = sqrt( (A232735+1)/2 ) = 2F1(-1/14,1/14;1/2;1/2).

Largest of the 12 real-valued roots of 4096*x^12 -12288*x^10 +13568*x^8 -6656*x^6 +1376*x^4 -96*x^2 +1 =0.

Example

0.99371220989324258353314824194737869715263549578207...

Mathematica

First[RealDigits[Cos[Pi/28], 10, 100]] (* Paolo Xausa, Nov 17 2025 *)

Crossrefs

Cf. A132744.

Sequence in context: A340628 A226204 A296454 * A179102 A153505 A088398

Adjacent sequences: A387445 A387446 A387447 * A387449 A387450 A387451

Keyword

nonn,cons,easy

Author

R. J. Mathar, Aug 29 2025

Status

approved