The OEIS is supported by the many generous donors to the OEIS Foundation.


(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A283416 Number of possible connected steric graphs with n nodes of degree less than 5. 1
1, 1, 2, 8, 43, 405 (list; graph; refs; listen; history; text; internal format)



This gives the number of hypothetical neutrally charged saturated carbon allotropes and hydrocarbons (alkanes, cycloalkanes, alkyl-cycloalkanes) with n carbon atoms satisfying the octet rule counting all isomers, except conformers.

Steric (three-dimensional) graphs can be represented as two-dimensional graphs provided that stereoisomers are taken into account. This means acting the group S_4 on the stereocenters (nodes with 4 different substituents) of each 2D graph and counting all of the resulting non-symmetric molecules.

Many of those "theoretical" molecules are to be discovered and some may not exist due to their strained geometries.

The terms of this sequence (and related ones) were found by drawing and counting the molecules in the PDFs below. If there are any missing molecules you can contact me. I'll add them in the PDF and update the data section.


Table of n, a(n) for n=1..6.

Natan Arie' Consigli, Illustration of a(5) and a(6)


a(4) = 8 because there are eight structures with 4 nodes (carbons) following the above rules: butane, isobutane, cyclobutane, methylcyclopropane, (r,r)-bicyclobutane, (s,s)-bicyclobutane, (r,r,r)-tetrahedrane, (s,s,s)-tetrahedrane.


Row sums of A280013.

Sequence in context: A276497 A324670 A334335 * A075817 A264565 A018985

Adjacent sequences:  A283413 A283414 A283415 * A283417 A283418 A283419




Natan Arie Consigli, Mar 07 2017



Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 23 20:29 EDT 2022. Contains 353993 sequences. (Running on oeis4.)