

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
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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



