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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A067608 Number of structural alkanes with combinatorial diameter n. 3
1, 1, 3, 6, 53, 496, 81096, 35292601, 211275732504203, 5013078952131335869356, 4188494841905497365271738826910705731652978, 13998172580873019733546655911268420464183123192214609601699428961 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

R. Davies and P. J. Freyd, C_{167}H_{336} is The Smallest Alkane with More Realizable Isomers than the Observable Universe has Particles, Journal of Chemical Education, Vol. 66, April 1989, pp. 278-281.

LINKS

Table of n, a(n) for n=1..12.

EXAMPLE

There are 53 such alkanes where the longest chain of carbon atoms is of length 5.

MATHEMATICA

rid[0]=1; rid[r_] := rid[r]=1+Binomial[rid[r-1]+2, 3]; rd[r_] := rid[r]-rid[r-1]; td[1]=1; td[r_] := If[EvenQ[r], Binomial[rd[r/2]+1, 2], Binomial[rid[(r-1)/2]+3, 4]-rd[(r-1)/2]Binomial[rid[(r-3)/2]+2, 3]-Binomial[rid[(r-3)/2]+3, 4]]; td/@Range[12]

CROSSREFS

Cf. A000602, A000628, A067609, A067610.

Sequence in context: A056437 A309320 A012275 * A023177 A132474 A032070

Adjacent sequences:  A067605 A067606 A067607 * A067609 A067610 A067611

KEYWORD

nonn

AUTHOR

Peter Freyd (pjf(AT)saul.cis.upenn.edu), Feb 02 2002

EXTENSIONS

Edited by Dean Hickerson, Feb 11 2002

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 6 15:14 EDT 2021. Contains 343586 sequences. (Running on oeis4.)