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A145426 Decimal expansion of Sum_{n>=0} (n!/(n+2)!)^2. 6
2, 8, 9, 8, 6, 8, 1, 3, 3, 6, 9, 6, 4, 5, 2, 8, 7, 2, 9, 4, 4, 8, 3, 0, 3, 3, 3, 2, 9, 2, 0, 5, 0, 3, 7, 8, 4, 3, 7, 8, 9, 9, 8, 0, 2, 4, 1, 3, 5, 9, 6, 8, 7, 5, 4, 7, 1, 1, 1, 6, 4, 5, 8, 7, 4, 0, 0, 1, 4, 9, 4, 0, 8, 0, 6, 4, 0, 1, 7, 4, 7, 6, 6, 7, 2, 5, 7, 8, 0, 1, 2, 3, 9 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

Alexander Apelblat, Tables of Integrals and Series, Harri Deutsch, (1996), 4.1.31.

Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 2.19 Vallée's Constant, p. 161.

LINKS

Table of n, a(n) for n=0..92.

R. J. Mathar, Tightly circumscribed regular polygons, arXiv:1301.6293 [math.MG], 2013, value (A15).

FORMULA

Equals A002388/3-3 = Sum_{n>=1} 1/A002378(n)^2 = Sum_{n>=2} 1/A035287(n).

EXAMPLE

0.28986813369645287294483...

MAPLE

evalf(1/3*Pi^2-3) ;

CROSSREFS

Cf. A002388 (Pi^2), A002378 (oblong numbers), A035287.

Sequence in context: A081819 A296850 A021349 * A200499 A298525 A081101

Adjacent sequences:  A145423 A145424 A145425 * A145427 A145428 A145429

KEYWORD

cons,easy,nonn

AUTHOR

R. J. Mathar, Feb 08 2009

STATUS

approved

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Last modified May 18 23:41 EDT 2021. Contains 344009 sequences. (Running on oeis4.)