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 A103945 Number of rooted dual-unicursal n-edge maps in the plane (planar with a distinguished outside face). 1
 2, 14, 107, 844, 6757, 54522, 441863, 3589880, 29206025, 237780982, 1936486411, 15771410420, 128431734797, 1045618229234, 8510270668815, 69241255165936, 563154350637073, 4578526894227438, 37209886138826771, 302291556342169580 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES V. A. Liskovets and T. R. Walsh, Enumeration of unrooted maps on the plane, Rapport technique, UQAM, No. 2005-01, Montreal, Canada, 2005. LINKS V. A. Liskovets and T. R. Walsh, Counting unrooted maps on the plane, Advances in Applied Math., 36, No.4 (2006), 364-387. FORMULA a(n)=(n+2)*A069720(n)-A103944(n). MATHEMATICA A069720[n_] := 2^(n-1) Binomial[2n-1, n]; A103944[n_] := If[n == 1, 1, n Binomial[2n, n] Sum[Binomial[n-2, k] (1/(n + 1 + k) + n/(n + 2 + k)), {k, 0, n-2}]]; a[n_] := (n+2) A069720[n] - A103944[n]; Array[a, 20] (* Jean-François Alcover, Aug 28 2019 *) CROSSREFS Cf. A069720, A103944. Sequence in context: A074618 A108436 A088754 * A111713 A144278 A214766 Adjacent sequences:  A103942 A103943 A103944 * A103946 A103947 A103948 KEYWORD easy,nonn AUTHOR Valery A. Liskovets, Mar 17 2005 STATUS approved

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Last modified January 21 03:16 EST 2021. Contains 340332 sequences. (Running on oeis4.)