This site is supported by donations to The OEIS Foundation.

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A187928 Number of embeddings on the sphere of 2-connected planar graphs, minimum vertex degree 3, with n edges. 1
 1, 1, 4, 15, 42, 135, 440, 1480, 5106, 17890, 63264, 226018, 812354, 2936837, 10666188, 38901190, 142386358 (list; graph; refs; listen; history; text; internal format)
 OFFSET 10,3 COMMENTS The graphs are exactly 2-connected, not at least 2-connected.  The graphs were enumerated using plantri (by B.D. McKay & G. Brinkmann) for the purpose of finding compound perfect squared squares.  If all graphs with n edges are generated then all compound squares in order n-1 can be obtained from them. Graphs with minimum degree 3 are also called homeomorphically irreducible. LINKS Stuart Anderson, Compound Perfect Squared Squares B. D. McKay and G. Brinkmann, Plantri Guide Gunnar Brinkmann and Brendan McKay, Guide to using plantri [Cached copy, with permission] PROG use; plantri -p -c2 -m3 -e# -x -u -v n  ; or plantri -pc2m3e#xuv n to count graphs by node number (n) and edge number (#) CROSSREFS Cf. A034889, A181340, A187927, A021103. Sequence in context: A100503 A085829 A085567 * A213498 A240359 A282522 Adjacent sequences:  A187925 A187926 A187927 * A187929 A187930 A187931 KEYWORD nonn,more,hard AUTHOR Stuart E Anderson, Mar 16 2011 EXTENSIONS Corrected a(22) - Stuart E Anderson, Feb 24 2013 a(23)-a(26) from Lorenz Milla, Oct 08 2013 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.