OFFSET
0,9
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..500
EXAMPLE
a(7) = 1: 1234567.
a(8) = 7: 12345687, 12345786, 12346785, 12356784, 12456783, 13456782, 23456781.
MAPLE
b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
`if`(t=0, add(b(u-j, o+j-1, irem(t+1, 7)), j=1..u),
add(b(u+j-1, o-j, irem(t+1, 7)), j=1..o)))
end:
a:= n-> b(n, 0$2):
seq(a(n), n=0..35);
MATHEMATICA
nmax = 30; CoefficientList[Series[1 + Sum[(x^(7 - k) * HypergeometricPFQ[{1}, {8/7 - k/7, 9/7 - k/7, 10/7 - k/7, 11/7 - k/7, 12/7 - k/7, 13/7 - k/7, 2 - k/7}, -x^7/823543])/(7 - k)!, {k, 0, 6}] / HypergeometricPFQ[{}, {1/7, 2/7, 3/7, 4/7, 5/7, 6/7}, -x^7/823543], {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Apr 21 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 16 2014
STATUS
approved