|
| |
|
|
A000314
|
|
Number of mixed Husimi trees with n nodes; or labeled polygonal cacti with bridges.
(Formerly M3639 N1480)
|
|
12
|
|
|
|
1, 1, 1, 4, 31, 362, 5676, 111982, 2666392, 74433564, 2384579440, 86248530296, 3476794472064, 154579941792256, 7514932528712896, 396595845237540600, 22581060079942183936, 1379771773100463174608, 90059660791562688208128, 6253914166368448348512064
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,4
|
|
|
REFERENCES
|
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
|
LINKS
|
Alois P. Heinz, Table of n, a(n) for n = 0..100
G. W. Ford and G. E. Uhlenbeck, Combinatorial problems in the theory of graphs III, Proc. Nat. Acad. Sci. USA, 42 (1956), 529-535.
Index entries for sequences related to cacti
Index entries for sequences related to trees
|
|
|
FORMULA
|
a(n) = A035351/n, n>0. - Christian G. Bower, Nov 15 1998
|
|
|
MAPLE
|
A:= proc(n) option remember; if n<=0 then x else convert(series(x* exp((2*A(n-1) -A(n-1)^2)/ (2-2*A(n-1))), x=0, n+2), polynom) fi end: a:= n-> if n=0 then 1 else coeff(series(A(n-1), x=0, n+1), x, n)*(n-1)! fi: seq(a(n), n=0..30); # Alois P. Heinz, Aug 20 2008
|
|
|
MATHEMATICA
|
A[n_] := A[n] = If[n <= 0, x, Normal[Series[x*Exp[(2*A[n-1]-A[n-1]^2)/ (2-2*A[n-1])], {x, 0, n+2}]]]; a[n_] := If[n == 0, 1, Coefficient [Series[A[n-1], {x, 0, n+1}], x, n]*(n-1)!]; Table [a[n], {n, 0, 30}] (* Jean-François Alcover, Mar 03 2014, after Alois P. Heinz *)
|
|
|
CROSSREFS
|
Cf. A000083, A000237, A035082, A035349-A035357.
Sequence in context: A201628 A086677 A016036 * A128709 A138860 A198865
Adjacent sequences: A000311 A000312 A000313 * A000315 A000316 A000317
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
N. J. A. Sloane
|
|
|
EXTENSIONS
|
More terms from Christian G. Bower, Nov 15 1998
|
|
|
STATUS
|
approved
|
| |
|
|
