A298738 Decimal expansion of (1/2)(1 + sqrt(7 + 2*sqrt(5))).

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

Offset

1,1

Links

Clark Kimberling, Table of n, a(n) for n = 1..10000

Index entries for algebraic numbers, degree 4.

Formula

Root of x^4-2*x^3-2*x^2+3*x+1. - R. J. Mathar, May 02 2026

Example

constant = 2.1935270853310539386... = positive zero of x^2 - x - r^2, where r = golden ratio = (1+ sqrt(5))/2; see A001622.

Mathematica

r = (1/2)*(1 + Sqrt[7 + 2*Sqrt[5]])
RealDigits[N[r, 100], 10][[1]];  (* A298738 *)
RealDigits[(1+Sqrt[7+2*Sqrt[5]])/2, 10, 120][[1]] (* Harvey P. Dale, Jun 13 2025 *)

Crossrefs

Cf. A001622, A190157, A298522, A298523, A275828.

Sequence in context: A355881 A095888 A160510 * A124776 A099285 A249264

Adjacent sequences: A298735 A298736 A298737 * A298739 A298740 A298741

Keyword

nonn,easy,cons

Author

Clark Kimberling, Feb 13 2018

Status

approved