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A067648 Number of knot diagrams of type 2PI with n crossings and two outgoing strings. 2
0, 2, 0, 2, 4, 12, 60, 226, 1076, 5156, 24984, 128548, 663040, 3514968, 18918792, 103123906, 569877652, 3180066004, 17921451960, 101842206548, 583109887600, 3361640932872, 19499226668816 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..22.

J. L. Jacobsen and P. Zinn-Justin, A Transfer Matrix approach to the Enumeration of Knots

CROSSREFS

Cf. A054993, A067647.

Sequence in context: A274414 A079550 A226430 * A279327 A052438 A324045

Adjacent sequences:  A067645 A067646 A067647 * A067649 A067650 A067651

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 05 2002

EXTENSIONS

Reference gives two further terms.

STATUS

approved

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Last modified June 16 11:12 EDT 2019. Contains 324152 sequences. (Running on oeis4.)