login
A117871
Decimal expansion of Sum_{i>=1} 1/A092143(i).
5
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
OFFSET
1,2
COMMENTS
It follows from the Mingarelli reference that this number is irrational.
LINKS
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
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