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A029758 Number of AVL trees of height n. 4
1, 1, 3, 15, 315, 108675, 11878720875, 141106591466142946875, 19911070158545297149037891328865229296875, 396450714858513044552818188364610837019719636049876979456842033610756600341796875 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

D. E. Knuth, Art of Computer Programming, Vol. 3, Sect. 6.2.3 (7) and (8).

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..12

Index entries for sequences related to rooted trees

FORMULA

a(n+1) = a(n)^2 + 2*a(n)*a(n-1).

EXAMPLE

G.f. = 1 + x + 3*x^2 + 15*x^3 + 315*x^4 + 108675*x^5 + 11878720875*x^6 + ...

MAPLE

A029758 := proc(n) option remember; if n <= 1 then RETURN(1); else A029758(n-1)^2+2*A029758(n-1)*A029758(n-2); fi; end;

MATHEMATICA

a[0] = a[1] = 1; a[n_] := a[n] = a[n-1]^2 + 2*a[n-1]*a[n-2]; Table[a[n], {n, 0, 9}] (* Jean-Fran├žois Alcover, Feb 13 2015 *)

PROG

(PARI) {a(n) = if( n<2, n>=0, a(n-1) * (a(n-1) + 2*a(n-2)))}; /* Michael Somos, Feb 07 2004 */

CROSSREFS

Cf. A029846.

Row sums of A143897. - Alois P. Heinz, Jun 01 2009

Sequence in context: A070234 A036279 A156769 * A103031 A012474 A296940

Adjacent sequences:  A029755 A029756 A029757 * A029759 A029760 A029761

KEYWORD

easy,nonn

AUTHOR

Don Knuth

EXTENSIONS

More terms from N. J. A. Sloane.

STATUS

approved

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Last modified February 21 12:10 EST 2018. Contains 299411 sequences. (Running on oeis4.)