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A131595 Decimal expansion of 3*(sqrt(25 + 10*sqrt(5))), the surface area of a regular dodecahedron with edges of unit length. 8
2, 0, 6, 4, 5, 7, 2, 8, 8, 0, 7, 0, 6, 7, 6, 0, 3, 0, 7, 3, 1, 0, 8, 1, 4, 3, 7, 2, 8, 6, 6, 3, 3, 1, 5, 1, 9, 2, 8, 8, 8, 4, 9, 0, 0, 4, 0, 1, 2, 2, 3, 7, 9, 9, 5, 0, 4, 8, 5, 1, 3, 6, 4, 8, 4, 2, 8, 6, 4, 2, 7, 9, 0, 6, 5, 0, 7, 5, 9, 4, 7, 7, 5, 9, 8, 9, 2, 9, 4, 8, 9, 6, 6, 5, 1, 0, 5, 2, 8, 8, 5, 9, 2, 6, 5, 1, 3, 7, 0, 5, 5, 4, 1, 7, 7, 0, 0, 3, 1, 9 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Surface area of a regular dodecahedron: A = 3*(sqrt(25 + 10*sqrt(5)))* a^2, where 'a' is the edge.

LINKS

G. C. Greubel, Table of n, a(n) for n = 2..10001

Eric Weisstein's World of Mathematics, Dodecahedron

Wikipedia, Platonic solid

FORMULA

From Stanislav Sykora, Nov 30 2013: (Start)

Equals 15/tan(Pi/5).

Equals 15*phi/xi, where phi is the golden ratio (A001622) and xi its associate (A182007). (End)

EXAMPLE

20.64572880706760307310814372866331519288849004012237995...

MAPLE

evalf(3*(sqrt(25+10*sqrt(5))), 130); # Muniru A Asiru, Nov 02 2018

MATHEMATICA

RealDigits[3  Sqrt[25+10Sqrt[5]], 10, 120][[1]]  (* Harvey P. Dale, Jun 21 2011 *)

PROG

(PARI) default(realprecision, 100); 3*(sqrt(25 + 10*sqrt(5))) \\ G. C. Greubel, Nov 02 2018

(MAGMA) SetDefaultRealField(RealField(100)); 3*(Sqrt(25 + 10*Sqrt(5))); // G. C. Greubel, Nov 02 2018

CROSSREFS

Cf. A102769, A001622 (phi), A182007 (associate of phi), A010527 (icosahedron/10), A010469 (octahedron), A002194 (tetrahedron). - Stanislav Sykora, Nov 30 2013

Sequence in context: A136656 A256850 A242561 * A290826 A124228 A115879

Adjacent sequences:  A131592 A131593 A131594 * A131596 A131597 A131598

KEYWORD

nonn,cons,easy

AUTHOR

Omar E. Pol, Aug 30 2007

EXTENSIONS

More terms from Harvey P. Dale, Jun 21 2011

STATUS

approved

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Last modified December 19 02:36 EST 2018. Contains 318245 sequences. (Running on oeis4.)