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A283049
Numbers of configurations of A'Campo forests with co-dimension 1 and degree n>0.
4
0, 4, 48, 480, 4560, 42504, 393120, 3624768, 33390720, 307618740, 2835722032, 26162863584, 241614915360, 2233533229200, 20667453710400, 191422799835264, 1774573628661504, 16465220088660432, 152894968403313600, 1420856831349155200, 13213537097286612240
OFFSET
0,2
COMMENTS
We can prove this using generating functions. a(n) is given also by 4*binomial(4n,n-2), for n>1.
LINKS
N. Combe, V. Jugé, Counting bi-colored A'Campo forests, arXiv:1702.07672 [math.AG], 2017.
FORMULA
a(n) = 4*binomial(4n,n-2), for n>1.
EXAMPLE
For n=2 the a(2)=4 solutions are the number of A'Campo forests with co-dimension 1 and degree 2.
MATHEMATICA
Table[4*Binomial[4n, n-2], {n, 1, 23}] (* Indranil Ghosh, Feb 28 2017 *)
PROG
(PARI) a(n) = 4*binomial(4*n, n-2) \\ Indranil Ghosh, Feb 28 2017
CROSSREFS
Sequence in context: A299603 A026942 A264727 * A159903 A099671 A196963
KEYWORD
nonn
AUTHOR
Noemie Combe, Feb 27 2017
STATUS
approved