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A007171 Number of Q-graphs with 2n edges.
(Formerly M1296)
0
1, 2, 4, 16, 89, 579, 3989, 28630, 210865, 1584308, 12091902, 93483120, 730503054, 5760438853, 45780146521, 366304396662, 2948412461685, 23857049238752, 193944769559906, 1583294537879106, 12974430494985262, 106685110047676402 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..22.

R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math. 31 (1986) no 1, 47-63.

FORMULA

a(1) = 1, a(n) = A007170(n) + (A003169(n-1) + A007165(n-1)) / 2. - Sean A. Irvine, Nov 07 2017

CROSSREFS

Cf. A003169, A007165, A007170.

Sequence in context: A212432 A013115 A291286 * A058136 A156335 A026089

Adjacent sequences:  A007168 A007169 A007170 * A007172 A007173 A007174

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

a(9) corrected and more terms from Sean A. Irvine, Nov 07 2017

STATUS

approved

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Last modified January 23 19:34 EST 2020. Contains 331175 sequences. (Running on oeis4.)