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A125205 Triangular array T(n,k) (n>=1, 0<=k<=n(n-1)/2) giving the total number of connected components in all subgraphs (V,E') with |E'|=k of the complete labeled graph K_n=(V,E). 5
1, 2, 1, 3, 6, 3, 1, 4, 18, 30, 24, 15, 6, 1, 5, 40, 135, 250, 295, 282, 215, 120, 45, 10, 1, 6, 75, 420, 1385, 3015, 4800, 6365, 7170, 6705, 5065, 3009, 1365, 455, 105, 15, 1, 7, 126, 1050, 5355, 18690, 47880, 96796, 166890, 251370, 329945, 373947, 362292, 297115 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..54.

FORMULA

G.f.: Sum_{n,k} T(n,k)*x^n/n!*y^k=(F(x,y)-1)*exp(F(x,y)-1)=G(x,y)*log(G(x,y)) where G(x,y)=Sum_{n=0..oo} (1+y)^(n(n-1)/2)*x^n/n! and F(x,y)=1+log(G(x,y)) is g.f. of A062734.

EXAMPLE

The array starts with

1

2, 1

3, 6, 3, 1

4, 18, 30, 24, 15, 6, 1

5, 40, 135, 250, 295, 282, 215, 120, 45, 10, 1

...

T(3,1)=6 since there are three different subgraphs of K_3 with one edge and each subgraph has two connected components.

PROG

(PARI) { G=sum(n=0, 6, (1+y)^(n*(n-1)/2)*x^n/n!); K=G*log(G); for(n=1, 6, print(Vecrev(n!*polcoeff(K, n, x)))) }

CROSSREFS

Cf. A062734.

Cf. A125206 (row-reversed version), A125207 (row sums).

Sequence in context: A006895 A202204 A289815 * A125206 A221918 A193897

Adjacent sequences:  A125202 A125203 A125204 * A125206 A125207 A125208

KEYWORD

nonn,tabf

AUTHOR

Max Alekseyev, Nov 23 2006

STATUS

approved

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Last modified March 4 07:25 EST 2021. Contains 341781 sequences. (Running on oeis4.)