A117871 - OEIS

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A117871

Decimal expansion of Sum_{i>=1} 1/A092143(i).

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

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OFFSET

1,2

COMMENTS

It follows from the Mingarelli reference that this number is irrational.

LINKS

Table of n, a(n) for n=1..105.

Angelo B. Mingarelli, Abstract factorials of arbitrary sets of integers, arXiv:0705.4299 [math.NT], 200-2012.

EXAMPLE

1.6917992098217123513392618067876318698236937629258191345569...

MAPLE

Digits := 60 : A092143 := proc(n) option remember ; local dvs ; if n = 1 then 1 ; else dvs := numtheory[divisors](n) ; A092143(n-1)*mul(i, i=dvs) ; fi ; end: A129635 := proc(isum) a := 0.0 ; for i from 1 to isum do a := a+1.0/A092143(i) ; print(evalf(a)) ; od ; RETURN(a) ; end: A129635(200) ; # R. J. Mathar, Sep 02 2007

MATHEMATICA

digits = 105; A092143[m_] := For[n = k = 1, k <= m, k++, Do[n = n*d, {d, Divisors[k]}]; If[k == m, Return[n]]] ; rd[j_] := rd[j] = RealDigits[ N[ Sum[ 1/A092143[m], {m, 1, 2^j}], digits]][[1]]; rd[j = 4]; While[ rd[j] != rd[j - 1], j++]; rd[j] (* Jean-François Alcover, Oct 30 2012 *)

CROSSREFS

Cf. A092143.

Sequence in context: A198504 A357066 A179593 * A011454 A274480 A115145

Adjacent sequences: A117868 A117869 A117870 * A117872 A117873 A117874

KEYWORD

cons,easy,nonn

AUTHOR

Jonathan Vos Post, May 31 2007

EXTENSIONS

More terms from R. J. Mathar, Sep 02 2007

Edited by N. J. A. Sloane, Sep 16 2007 and May 06 2008

More digits from R. J. Mathar, Jul 12 2009

STATUS

approved