The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A001384 Number of n-node trees of height at most 4. (Formerly M1172 N0449) 4
 1, 1, 1, 2, 4, 9, 19, 42, 89, 191, 402, 847, 1763, 3667, 7564, 15564, 31851, 64987, 132031, 267471, 539949, 1087004, 2181796, 4367927, 8721533, 17372967, 34524291, 68456755, 135446896, 267444085, 527027186, 1036591718, 2035083599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS a(n+1) is also the number of n-vertex graphs that do not contain a P_4, C_4, or K_5 as induced subgraph (K_5-free trivially perfect graphs, cf. A123467). - Falk Hüffner, Jan 10 2016 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 N. J. A. Sloane, Table of n, a(n) for n=0..200 INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 63 J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478. N. J. A. Sloane, Transforms FORMULA Take Euler transform of A001383 and shift right. (Christian G. Bower). MAPLE For Maple program see link in A000235. with(numtheory): etr:= proc(p) local b; b:=proc(n) option remember; local d, j; if n=0 then 1 else add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n)/n fi end end: A000041:= etr(n->1): b1:= etr(k-> A000041(k-1)): A001383:= n->`if`(n=0, 1, b1(n-1)): b2:= etr(A001383): a:= n->`if`(n=0, 1, b2(n-1)): seq(a(n), n=0..40); # Alois P. Heinz, Sep 08 2008 MATHEMATICA Prepend[Nest[CoefficientList[Series[Product[1/(1-x^i)^#[[i]], {i, 1, Length[#]}], {x, 0, 40}], x]&, {1}, 4], 1] (* Geoffrey Critzer, Aug 01 2013 *) CROSSREFS See A001383 for details. Sequence in context: A305380 A275862 A036622 * A089941 A307464 A127681 Adjacent sequences:  A001381 A001382 A001383 * A001385 A001386 A001387 KEYWORD nonn AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 26 22:58 EDT 2020. Contains 334634 sequences. (Running on oeis4.)