OFFSET
0,2
COMMENTS
Equivalently, the number of paths of length 19n in Z^19 from {0}^19 to {n}^19. - Andrew Howroyd, Nov 01 2018
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..40
Gilbert Labelle and Annie Lacasse, Closed paths whose steps are roots of unity, in FPSAC 2011, Reykjavik, Iceland DMTCS proc. AO, 2011, 599-610.
FORMULA
a(n) = (19*n)!/(n!)^19. - Andrew Howroyd, Nov 01 2018
PROG
(PARI) a(n) = (19*n)!/(n!)^19; \\ Andrew Howroyd, Nov 01 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Simon Plouffe, Oct 30 2011
EXTENSIONS
Sequence redefined and a(2)-a(4) from Andrew Howroyd, Nov 01 2018
STATUS
approved