|
|
A259452
|
|
Number of 5 up, 5 down, 5 up, ... permutations of length 5n+1.
|
|
1
|
|
|
1, 1, 252, 578005, 6190034016, 214265281290061, 19157603395806362772, 3800502511986185228829385, 1498722661993096106927612109936, 1081056808393919319749313795137642521, 1336319624105519211256870506149168604698792
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
REFERENCES
|
P. R. Stein, personal communication.
|
|
LINKS
|
|
|
MAPLE
|
b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(`if`(
t=5, b(o-j, u+j-1, 1), b(u+j-1, o-j, t+1)), j=1..o))
end:
a:= n-> b(0, 5*n+1, 0):
|
|
MATHEMATICA
|
k = 5; b[u_, o_, t_] := b[u, o, t] = If[u + o == 0, 1, Sum[If[t == k, b[o - j, u + j - 1, 1], b[u + j - 1, o - j, t + 1]], {j, 1, o}]]; Array[b[0, k # + 1, 0] &, 10] (* Michael De Vlieger, Oct 15 2017, after Jean-François Alcover at A005983 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|