A222392 -id:A222392 - cp's OEIS frontend

A222391 Decimal expansion of e^2/sqrt(Pi).

4, 1, 6, 8, 8, 2, 8, 4, 8, 3, 2, 6, 6, 6, 9, 2, 2, 3, 0, 4, 2, 1, 3, 0, 3, 9, 0, 7, 7, 5, 2, 3, 1, 0, 2, 6, 0, 3, 8, 6, 6, 6, 4, 6, 8, 1, 1, 4, 8, 4, 9, 9, 6, 3, 7, 8, 3, 0, 0, 0, 8, 9, 5, 4, 6, 2, 4, 0, 4, 3, 2, 2, 7, 2, 0, 1, 5, 3, 6, 0, 9, 2, 7, 9, 8, 1, 9

Offset: 1

Bruno Berselli, Mar 19 2013

			4.1688284832666922304213039077523102603866646811484996378300089546240432...

G. C. Greubel, Table of n, a(n) for n = 1..5000

Cf. A072334, A087197, A222392.
Cf. A096789: Sum_{n >= 1} 1/(Gamma(n)*Gamma(n+1)).
Cf. A035009 (see fourth comment).

Digits:=100: evalf(exp(1)^2/sqrt(Pi)); # Wesley Ivan Hurt, Jan 09 2017

Mathematica
```
RealDigits[E^2/Sqrt[Pi], 10, 90][[1]]
```

(exp(1))^2/sqrt(Pi) \\ G. C. Greubel, Jan 09 2017

Equals A072334*A087197.

Equals decimal expansion of Sum_{n >= 1} 1/(Gamma(n/2)*Gamma((n+1)/2)).

A378942 Decimal expansion of (1/sqrt(Pi) + e*erfc(-1))/2.

Original entry on oeis.org

2, 7, 8, 6, 5, 8, 4, 8, 3, 2, 1, 5, 5, 0, 1, 9, 8, 7, 6, 6, 2, 8, 9, 5, 2, 0, 2, 4, 8, 8, 7, 7, 9, 1, 2, 0, 0, 2, 6, 9, 1, 9, 2, 6, 5, 6, 7, 8, 2, 3, 3, 2, 6, 7, 1, 5, 1, 6, 2, 4, 0, 6, 0, 3, 2, 0, 9, 1, 4, 5, 1, 5, 3, 6, 6, 4, 1, 7, 2, 6, 7, 9, 2, 1, 1, 2, 2, 9, 9, 6, 2, 2, 6, 6, 5, 2, 6, 8, 4, 2

Offset: 1

Stefano Spezia, Dec 11 2024

			2.7865848321550198766289520248877912002691926567823...

Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 4.6, p. 262.

Cf. A001113, A019739, A087197, A087198, A099286, A222392.

RealDigits[(1/Sqrt[Pi]+E Erfc[-1])/2,10,100][[1]]

Equals (1 + e*sqrt(Pi)*(1 + erf(1)))/(2*sqrt(Pi)).

Equals A222392 / 2. - Amiram Eldar, Feb 15 2025

cp's OEIS Frontend

A222391 Decimal expansion of e^2/sqrt(Pi).

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