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 A164102 Decimal expansion of 2*Pi^2. 12
 1, 9, 7, 3, 9, 2, 0, 8, 8, 0, 2, 1, 7, 8, 7, 1, 7, 2, 3, 7, 6, 6, 8, 9, 8, 1, 9, 9, 9, 7, 5, 2, 3, 0, 2, 2, 7, 0, 6, 2, 7, 3, 9, 8, 8, 1, 4, 4, 8, 1, 5, 8, 1, 2, 5, 2, 8, 2, 6, 6, 9, 8, 7, 5, 2, 4, 4, 0, 0, 8, 9, 6, 4, 4, 8, 3, 8, 4, 1, 0, 4, 8, 6, 0, 0, 3, 5, 4, 6, 8, 0, 7, 4, 3, 7, 1, 0, 4, 4, 6, 3, 6, 4, 8, 0 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS Surface area of the 4-dimensional unit sphere. The volume of the 4-dimensional unit sphere is a fourth of this, A102753. Also decimal expansion of Pi^2/5 = 1.973920..., with offset 1. - Omar E. Pol, Oct 04 2011 REFERENCES L. A. Santalo, Integral Geometry and Geometric Probability, Addison-Wesley, 1976, see p. 15. [From N. J. A. Sloane, Sep 16 2009] LINKS G. C. Greubel, Table of n, a(n) for n = 2..5000 Yann Bernard, Autour des surfaces de Willmore, Images des MathÃ©matiques, CNRS, 2014 (in French). Fernando C. Marques and AndrÃ© Neves, Min-Max theory and the Willmore conjecture, arXiv:1202.6036 [math.DG], 2012-2013. Eric Weisstein's World of Mathematics Hypersphere Wikipedia, Hypersphere Wikipedia, Willmore conjecture FORMULA Equals 2*A002388 = 4*A102753. EXAMPLE 19.739208802178717237668981... MATHEMATICA RealDigits[2*Pi^2, 10, 120][[1]] (* Harvey P. Dale, Apr 19 2012 *) PROG (PARI) 2*Pi^2 \\ Charles R Greathouse IV, Jan 24 2014 CROSSREFS Cf. A002388, A091476, A013661. Sequence in context: A135449 A060388 A081821 * A105532 A111471 A078527 Adjacent sequences:  A164099 A164100 A164101 * A164103 A164104 A164105 KEYWORD cons,nonn,easy,changed AUTHOR R. J. Mathar, Aug 10 2009 STATUS approved

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