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Revision History for A303840 (Underlined text is an addition; strikethrough text is a deletion.)

Showing entries 1-10 | older changes
A303840 Unlabeled trees with n nodes rooted at 2 indistinguishable roots that are leaves.
(history; published version)
#14 by Joerg Arndt at Tue Jun 25 01:30:10 EDT 2024
STATUS

reviewed

approved

#13 by Michel Marcus at Tue Jun 25 00:58:42 EDT 2024
STATUS

proposed

reviewed

#12 by Jon E. Schoenfield at Tue Jun 25 00:17:06 EDT 2024
STATUS

editing

proposed

#11 by Jon E. Schoenfield at Tue Jun 25 00:16:51 EDT 2024
EXAMPLE

a(2)=a(3)=1, because the two roots must be the (all) the leaves. a(4)=2 (one pattern from the linear tree, one from the star tree). a(6)=10: 1 pattern from n-Hexane. 2 patterns from 2-Methyl-Pentane. 2 patterns from (2,3)-Bimethyl-Butane. 1 pattern from the star graph. 2 patterns from 3-Methyl-Pentane. 2 patterns from (2,2)-Bimethyl-Butane.

STATUS

approved

editing

#10 by R. J. Mathar at Fri May 04 04:44:15 EDT 2018
STATUS

editing

approved

#9 by R. J. Mathar at Fri May 04 04:44:11 EDT 2018
CROSSREFS

Cf. A303833 (roots mayneed not be leaves), A055290 (cardinality of candidates).

STATUS

approved

editing

#8 by R. J. Mathar at Tue May 01 13:00:17 EDT 2018
STATUS

proposed

approved

#7 by R. J. Mathar at Tue May 01 11:35:00 EDT 2018
STATUS

editing

proposed

Discussion
Tue May 01 12:23
Omar E. Pol: I think the Name should starts with a(n) is the number of ..."
#6 by R. J. Mathar at Tue May 01 11:34:49 EDT 2018
EXAMPLE

a(2)=a(3)=1, because the two roots must be the (all) leaves. a(4)=2 (one pattern from the linear tree, one from the star tree).). a(6)=10: 1 pattern from n-Hexane. 2 patterns from 2-Methyl-Pentane. 2 patterns from (2,3)-Bimethyl-Butane. 1 pattern from the star graph. 2 patterns from 3-Methyl-Pentane. 2 patterns from (2,2)-Bimethyl-Butane.

#5 by R. J. Mathar at Tue May 01 11:28:21 EDT 2018
DATA

0, 1, 1, 2, 4, 10, 24, 63, 164, 444, 1204, 3328, 9233, 25865, 72734, 205656, 583320, 1660318, 4737540, 13551165, 38837535, 111512229, 320681604, 923528963, 2663057582, 7688068638, 22218350303, 64272720521, 186091334380, 539237928902, 1563731491958, 4537823968645, 13176960639940, 38286514506439, 111306880581963

MAPLE

a000081 := [1, 1, 2, 4, 9, 20, 48, 115, 286, 719, 1842, 4766, 12486, 32973, 87811, 235381, 634847, 1721159, 4688676, 12826228,

35221832, 97055181, 268282855, 743724984, 2067174645, 5759636510, 16083734329, 45007066269, 126186554308, 354426847597,

997171512998, 2809934352700, 7929819784355, 22409533673568, 63411730258053, 179655930440464, 509588049810620, 1447023384581029,

4113254119923150, 11703780079612453, 33333125878283632] ;

g81 := add( op(i, a000081)*x^i, i=1..nops(a000081) ) ;

g81fin := x ;

g := 0 ;

nmax := nops(a000081) ;

for m from 0 to nmax do

mhalf := floor(m/2) ;

ghalf := g81^mhalf*g81fin ;

gcyc := (ghalf^2+subs(x=x^2, ghalf))/2 ;

if type(m, odd) then

gcyc := gcyc*g81 ;

end if;

g := g+gcyc ;

end do:

taylor(g, x=0, nmax) ;

gfun[seriestolist](%) ;

CROSSREFS

Cf. A303833 (roots may not be leaves), A055290. (cardinality of candidates).

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Last modified August 29 23:09 EDT 2024. Contains 375519 sequences. (Running on oeis4.)