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A309994 Number of forests of rooted trees with 2n colored nodes using exactly n colors. 2
1, 2, 89, 14845, 5613775, 3809941836, 4073969863427, 6316651717425358, 13407079935176225215, 37344967651943608528498, 132181958309965092862822183, 579566807739313784043087337938, 3083812115454145185391757131500066, 19577110356940490275990571617295644659 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..187

FORMULA

a(n) = A256064(2*n+1,n).

MAPLE

b:= proc(n, k) option remember; `if`(n<2, n, (add(add(d*b(d, k),

      d=numtheory[divisors](j))*b(n-j, k)*k, j=1..n-1))/(n-1))

    end:

a:= n-> add(b(2*n+1, n-i)*(-1)^i*binomial(n, i), i=0..n):

seq(a(n), n=0..15);

CROSSREFS

Cf. A256064.

Sequence in context: A226768 A246871 A024239 * A256962 A266807 A076532

Adjacent sequences:  A309991 A309992 A309993 * A309995 A309996 A309997

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 26 2019

STATUS

approved

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Last modified January 25 03:49 EST 2020. Contains 331241 sequences. (Running on oeis4.)