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 A005628 Number of chiral planted trees with n nodes. (Formerly M1641) 1
 0, 0, 0, 0, 2, 6, 20, 60, 176, 510, 1484, 4314, 12624, 37126, 109864, 326958, 978528, 2943384, 8895792, 27001378, 82281216, 251636434, 772101086, 2376186784, 7333094178, 22688117658, 70360646672, 218678194238, 681016789056 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. W. Robinson, F. Harary and A. T. Balaban, The numbers of chiral and achiral alkanes and monosubstituted alkanes, Tetrahedron 32 (1976), 355-361. R. W. Robinson, F. Harary and A. T. Balaban, Numbers of chiral and achiral alkanes and monosubstituted alkanes, Tetrahedron 32 (3) (1976), 355-361. (Annotated scanned copy) FORMULA a(n) = A000625(n)-A005627(n) (given as g(n)=s(n)-p(n) on p. 357 of the Robinson et al. paper). - Emeric Deutsch, May 16 2004 MAPLE s:=1:s:=1:for n from 0 to 60 do s[n+1/3]:=0 od:for n from 0 to 60 do s[n+2/3]:=0 od:for n from 1 to 55 do s[n+1]:=(2*n/3*s[n/3]+sum(j*s[j]*sum(s[k]*s[n-j-k], k=0..n-j), j=1..n))/n od:p:=1: for n from 0 to 50 do p[n+1]:=sum(s[k]*p[n-2*k], k=0..floor(n/2)) od:seq(s[n]-p[n], n=0..37); # here s[n]=A000625 and p[n]=A005627(n) CROSSREFS Cf. A000625, A005627. Sequence in context: A027294 A231538 A082045 * A000620 A081251 A134293 Adjacent sequences:  A005625 A005626 A005627 * A005629 A005630 A005631 KEYWORD nonn AUTHOR EXTENSIONS More terms from Emeric Deutsch, May 16 2004 STATUS approved

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Last modified September 29 21:59 EDT 2020. Contains 337432 sequences. (Running on oeis4.)