OFFSET
1,1
COMMENTS
a(n) is the number of lattice paths from (0,0) to (4n,n) using only the steps (1,0) and (0,1) and whose only lattice points on the line y = x/4 are the path's endpoints.
MATHEMATICA
Array[4 Binomial[5 #, #]/(5 # - 1) &, 20] (* Michael De Vlieger, Aug 21 2020 *)
PROG
(PARI) a(n) = {4*binomial(5*n, n)/(5*n-1)} \\ Andrew Howroyd, Aug 21 2020
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lucas A. Brown, Aug 21 2020
STATUS
approved