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A221209 Decimal expansion of two times the Catalan constant. 2
1, 8, 3, 1, 9, 3, 1, 1, 8, 8, 3, 5, 4, 4, 3, 8, 0, 3, 0, 1, 0, 9, 2, 0, 7, 0, 2, 9, 8, 6, 4, 7, 6, 8, 2, 2, 1, 5, 4, 8, 2, 9, 8, 7, 4, 8, 5, 6, 3, 3, 4, 4, 2, 6, 8, 5, 3, 2, 9, 9, 6, 2, 3, 9, 2, 4, 3, 5, 2, 6, 0, 3, 9, 5, 5, 2, 5, 0, 9, 5, 3, 8, 9, 5, 8, 7, 1, 3, 0, 2, 5, 8, 5, 2, 2, 3, 0, 2, 1, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Equals the integral of x/cosh(x) dx from x=0 to x=infinity.

REFERENCES

Gradsteyn, Rzyhik, Table of integrals, series and products, 5th edition, eq. (3.521.2).

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

FORMULA

Equals 2*A006752.

EXAMPLE

1.83193118835443803010920702986476822154...

MAPLE

evalf(2*Catalan) ;

MATHEMATICA

RealDigits[2 Catalan, 10, 100][[1]] (* Bruno Berselli, Feb 21 2013 *)

PROG

(PARI) default(realprecision, 100); 2*Catalan \\ G. C. Greubel, Aug 25 2018

(MAGMA) SetDefaultRealField(RealField(100)); R:=RealField(); 2*Catalan(R); // G. C. Greubel, Aug 25 2018

CROSSREFS

Sequence in context: A097890 A088453 A019782 * A056030 A195473 A195728

Adjacent sequences:  A221206 A221207 A221208 * A221210 A221211 A221212

KEYWORD

nonn,cons,easy

AUTHOR

R. J. Mathar, Feb 21 2013

STATUS

approved

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Last modified June 16 13:09 EDT 2019. Contains 324152 sequences. (Running on oeis4.)