A283743 - OEIS

A283743

Decimal expansion of Ei(1)/e, where Ei is the exponential integral function.

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

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OFFSET

0,1

COMMENTS

Can be considered the value of the divergent series -0! - 1! - 2! - ... ; see Lagarias reference Section 2.5. - Harry Richman, Jun 14 2020.

LINKS

Table of n, a(n) for n=0..101.

Jeffrey C. Lagarias, Euler's constant: Euler's work and modern developments, arXiv:1303.1856 [math.NT], 2013; Bull. Amer. Math. Soc., 50 (2013), 527-628.

Eric Weisstein's World of Mathematics, Exponential Integral

Eric Weisstein's World of Mathematics, Subfactorial

FORMULA

The real part of subfactorial(-1), that is the real part of Gamma(0,-1)/e.

EXAMPLE

0.6971748832350660687654786819195515953171754309543695173200548...

MATHEMATICA

RealDigits[ExpIntegralEi[1]/E, 10, 102][[1]]

PROG

(PARI) real(-eint1(-1)/exp(1)) \\ Michel Marcus, Jun 15 2020

CROSSREFS

Cf. A000166 (subfactorials), A061382 (Pi/e, the imaginary part of subfactorial(-1)), A091725 (Ei(1)), A073003 (-exp(1)*Ei(-1)).