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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A182157 The number of simple unlabelled graphs with n nodes having no components of size 1 or 2. 0
 2, 6, 21, 115, 865, 11180, 261434, 11719198, 1006730374, 164060444228, 50335933202664, 29003489553692808, 31397381477206877920, 63969560214904127718624, 245871831740396590978751568, 1787331725311868949057440884912, 24636021429527995774854054487417072, 645465483199214927570182087868056845600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS FORMULA O.g.f.: (1-x)*(1-x^2)* G(x) where G(x) is o.g.f. for A000088 MATHEMATICA nn = 20; g = Sum[NumberOfGraphs[n] x^n, {n, 0, nn}]; Drop[CoefficientList[Series[ g (1 - x) (1 - x^2), {x, 0, nn}], x], 3] CROSSREFS Sequence in context: A001349 A126060 A266934 * A110306 A028936 A066932 Adjacent sequences:  A182154 A182155 A182156 * A182158 A182159 A182160 KEYWORD nonn AUTHOR Geoffrey Critzer, Apr 15 2012 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.

Last modified July 28 06:33 EDT 2021. Contains 346317 sequences. (Running on oeis4.)