OFFSET
0,4
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..500
R. Kaye, A Gray code for set partitions, Info. Proc. Letts., 5 (1976), 171-173.
EXAMPLE
0, 1, 1, 4/5, 3/5, 6/13, 76/203, 279/877, 289/1035, 5296/21147, 26443/115975, ...
MATHEMATICA
Table[Numerator[Sum[BellB[j], {j, 0, n-1}]/BellB[n]], {n, 0, 30}] (* G. C. Greubel, Jul 25 2019 *)
PROG
(PARI) bell(n)=sum(k=0, n, stirling(n, k, 2));
vector(30, n, n--; numerator( sum(j=0, n-1, bell(j))/bell(n)) ) \\ G. C. Greubel, Jul 25 2019
(Magma) [0] cat [Numerator((&+[Bell(j): j in [0..n-1]])/Bell(n)): n in [1..30]]; // G. C. Greubel, Jul 25 2019
(Sage) [numerator(sum(bell_number(j) for j in (0..n-1))/bell_number(n)) for n in (0..30)] # G. C. Greubel, Jul 25 2019
(GAP) List([0..30], n-> NumeratorRat(Sum([0..n-1], j-> Bell(j))/Bell(n)) ); # G. C. Greubel, Jul 25 2019
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
N. J. A. Sloane, Jul 13 2011
STATUS
approved