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A000306 Number of trees of diameter 8.
(Formerly M3552 N1440)
3
1, 4, 19, 66, 219, 645, 1813, 4802, 12265, 30198, 72396, 169231, 387707, 871989, 1930868, 4215615, 9091410, 19389327, 40944999, 85691893, 177898521, 366614456, 750494796, 1526979694, 3089556090, 6219191608, 12460307373, 24856533408, 49387348955, 97765283686, 192870793594, 379287172272 (list; graph; refs; listen; history; text; internal format)
OFFSET
9,2
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
J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478.
PROG
(PARI)
sh_euler(p)={my(m=serprec(p, x)-1); x*exp(sum(i=1, m, subst(p+O(x^(1+m\i)), x, x^i)/i))}
lista(n)={my(s2=sh_euler(sh_euler(x+O(x*x^n))), s3=sh_euler(s2), s4=sh_euler(s3), r3=s3-s2, r4=s4-s3, t8=r4-r3*s3); Vec(t8)} \\ Christian Sievers, May 18 2023
CROSSREFS
Cf. A034853.
Sequence in context: A098813 A212039 A055485 * A100185 A357251 A291888
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Christian Sievers, May 18 2023
STATUS
approved

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Last modified April 23 03:30 EDT 2024. Contains 371906 sequences. (Running on oeis4.)