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A303829 Birooted graphs: number of unlabeled graphs with n nodes rooted at 2 indistinguishable roots. 4
0, 2, 6, 28, 148, 1144, 13128, 250240, 8295664, 494367376, 53628829952, 10655018252544, 3893626388008448, 2627758027841688960, 3289042848785452985600, 7666804477507744021487616, 33416397343695235205887366144, 273365202164844511328577434284160 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(n) = 2 * A126122(n). - Alois P. Heinz, May 01 2018

CROSSREFS

Cf. A303831 (connected), A303833 (trees), A126122.

Sequence in context: A225877 A228842 A218941 * A272820 A152393 A305199

Adjacent sequences:  A303826 A303827 A303828 * A303830 A303831 A303832

KEYWORD

nonn

AUTHOR

Brendan McKay, May 01 2018

STATUS

approved

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Last modified April 13 03:43 EDT 2021. Contains 342934 sequences. (Running on oeis4.)