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A055542 Total number of nodes in all simple graphs of n nodes. 2
1, 4, 12, 44, 170, 936, 7308, 98768, 2472012, 120051680, 11208976504, 1981094071104, 656526407783376, 406758179201296832, 471397289547064631520, 1024016251272440926318848, 4180909690610059855623236192, 32176399052621010609861807435264 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Graph Vertex
MAPLE
b:= proc(n, i, l) `if`(n=0 or i=1, 1/n!*2^((p-> add(ceil((p[j]-1)/2)
+add(igcd(p[k], p[j]), k=1..j-1), j=1..nops(p)))([l[], 1$n])),
add(b(n-i*j, i-1, [l[], i$j])/j!/i^j, j=0..n/i))
end:
a:= n-> n*b(n$2, []):
seq(a(n), n=1..20); # Alois P. Heinz, Aug 14 2019
MATHEMATICA
Needs["Combinatorica`"];
Table[NumberOfGraphs[n]*n, {n, 1, 20}] (* Geoffrey Critzer, Oct 13 2012 *)
CROSSREFS
Equals A000088(n)*n.
Sequence in context: A188632 A151460 A149364 * A149365 A000759 A076793
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sascha Kurz, Mar 25 2002
STATUS
approved

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Last modified March 28 13:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)