OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..922
FORMULA
a(n) = floor(A163456(n)) + [n mod 5 = 0]*A163455(n/5), with A163456(n) = binomial(5*n,n)/5 and A163455(n) = binomial(5*n-1,n) where [] is an Iverson bracket. - Georg Fischer, Mar 23 2019
EXAMPLE
a(2) = 9: {1,4}, {1,9}, {2,3}, {2,8}, {3,7}, {4,6}, {5,10}, {6,9}, {7,8}.
MAPLE
b:= proc(n, s, m, t) option remember; `if`(n=0, `if`(s=0 and t=0, 1, 0),
b(n-1, s, m, t)+`if`(t=0, 0, b(n-1, irem(s+n, m), m, t-1)))
end:
a:= n-> b(5*n, 0, 5, n):
seq(a(n), n=0..27);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 29 2018
STATUS
approved