The On-Line Encyclopedia of Integer Sequences (OEIS)

A094594 revision #13

A094594

Total number of edges in all connected labeled graphs on n nodes.

0, 1, 9, 144, 4140, 214200, 20264832, 3580049088, 1202974894656, 779257681804800, 982078160760512640, 2423077679970846226944, 11755368773275419420291072, 112487517660848696830655493120

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..14.

FORMULA

E.g.f.: A(x)/B(x), where A(x) is e.g.f. of A095351 and B(x) is e.g.f. of A006125. recurrence: a(n) = binomial(n, 2)*2^(binomial(n, 2) - 1) - Sum_{k=1..n-1} binomial(n, k)*2^binomial(n-k, 2)*a(k).

a(n) = Sum_{k=0..binomial(n,2)} A062734(n,k)*k. - Geoffrey Critzer, Sep 04 2013

MAPLE

a[1]:=0: for n from 1 to 16 do a[n]:= binomial(n, 2)*2^(binomial(n, 2)-1)-sum(binomial(n, k)*2^binomial(n-k, 2)*a[k], k=1..n-1) od: seq(a[n], n=1..16); # Emeric Deutsch

MATHEMATICA

nn=14; f[x_, y_]:=Sum[(1+y)^Binomial[n, 2]x^n/n!, {n, 0, nn}]; Drop[Range[0, nn]!CoefficientList[Series[D[Log[f[x, y]], y]/.y->1, {x, 0, nn}], x], 1] (* Geoffrey Critzer, Sep 04 2013 *)

CROSSREFS

Sequence in context: A069134 A034829 A162993 * A173213 A223371 A046529

Adjacent sequences: A094591 A094592 A094593 * A094595 A094596 A094597

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Jun 06 2004

EXTENSIONS

More terms from Emeric Deutsch, Dec 18 2004

STATUS

editing