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A198261 Triangular array read by rows T(n,k) is the number of simple labeled graphs on n nodes with exactly k isolated nodes, 0<=k<=n. 0
1, 0, 1, 1, 0, 1, 4, 3, 0, 1, 41, 16, 6, 0, 1, 768, 205, 40, 10, 0, 1, 27449, 4608, 615, 80, 15, 0, 1, 1887284, 192143, 16128, 1435, 140, 21, 0, 1, 252522481, 15098272, 768572, 43008, 2870, 224, 28, 0, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

Row sums = 2^binomial(n,2) = A006125(n).

First column (k=0) is A006129.

LINKS

Table of n, a(n) for n=0..44.

FORMULA

E.g.f. for column k: x^k/k! *A(x)/exp(x) where A(x) is the e.g.f. for A006125.

T(n,n) = 1 (the empty graph). - Geoffrey Critzer, Nov 11 2011

T(n,n-1) = 0. - Geoffrey Critzer, Nov 11 2011

EXAMPLE

1;

0,       1;

1,       0,      1;

4,       3,      0,     1;

41,      16,     6,     0,    1;

768,     205,    40,    10,   0,   1;

27449,   4608,   615,   80,   15,  0,  1;

1887284, 192143, 16128, 1435, 140, 21, 0, 1;

MATHEMATICA

g=Sum[2^Binomial[n, 2]x^n/n!, {n, 0, 20}]; Transpose[Table[Range[0, 10]! CoefficientList[Series[(x^n/n!)( g/Exp[x]), {x, 0, 10}], x], {n, 0, 8}]]//Grid

CROSSREFS

Sequence in context: A327125 A152148 A270708 * A284056 A296002 A227423

Adjacent sequences:  A198258 A198259 A198260 * A198262 A198263 A198264

KEYWORD

nonn,tabl

AUTHOR

Geoffrey Critzer, Oct 22 2011

STATUS

approved

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Last modified January 29 14:07 EST 2020. Contains 331338 sequences. (Running on oeis4.)