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REFERENCES
| G. Polya, Algebraische Berechnung der Anzahl der Isomeren einiger organischer Verbindungen, Zeit. f. Kristall., 93 (1936), 415-443.
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).
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MAPLE
| The following Maple commands are taken from the Chyzak web site:
with(combstruct);
gramm_Alkyl:=Alkyl=Prod(Carbon, Set(Alkyl, card<=3)), Carbon=Atom:
specs_Alkyl:=[Alkyl, {gramm_Alkyl}, unlabeled]:
gramm_S1_Alkyl:=S1_Alkyl[X]=Union(Prod(Carbon, S1_Alkyl[X], Set(Alkyl, card<=2)), Prod(Prod(Carbon, X), Set(Alkyl, card<=2))), X=Epsilon:
specs_S1_Alkyl:=[S1_Alkyl[X], {gramm_S1_Alkyl, gramm_Alkyl}, unlabeled]:
gramm_S2_Alkyl:=S2_Alkyl[X, Y]=Union(Prod(Carbon, S2_Alkyl[X, Y], Set(Alkyl, card<=2)), Prod(Carbon, Union(S1_Alkyl[X], X), Union(S1_Alkyl[Y], Y), Set(Alkyl, card<=1))):
specs_S2_Alkyl:=[S2_Alkyl[X, Y], {gramm_S2_Alkyl, gramm_S1_Alkyl, op(subs(X=Y, [gramm_S1_Alkyl])), gramm_Alkyl}, unlabeled]:
[seq(count(specs_S2_Alkyl, size=i), i=0..50)];
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