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A223095 Number of foldings of n labeled stamps in which both end leaves are inwards. 2
0, 0, 0, 2, 10, 40, 156, 546, 1986, 6716, 23742, 79472, 277178, 925588, 3205896, 10711486, 36963722, 123712788, 426075994, 1429030624, 4916833424, 16526958144, 56840484232, 191466923584, 658460090994, 2222507917328, 7644360501390, 25850724646008, 88938175307354 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Subset of foldings of n labeled stamps (A000136). - Stéphane Legendre, Apr 09 2013

LINKS

Stéphane Legendre, Table of n, a(n) for n = 1..42

S. Legendre, Foldings and Meanders, arXiv preprint arXiv:1302.2025 [math.CO], 2013.

S. Legendre, Foldings and Meanders, Aust. J. Comb. 58(2), 275-291, 2014.

Index entries for sequences obtained by enumerating foldings

FORMULA

a(n) = A223094(n) - A223093(n). - Andrew Howroyd, Dec 06 2015

a(n) = A000136(n) + A077014(n) - 2 * A000682(n). - Andrew Howroyd, Dec 06 2015

A217318(n) = a(n) if n is odd and A217318(n) = (1/2)*a(n) if n is even. - Stéphane Legendre, Jan 13 2014

MATHEMATICA

A217318 = Import["https://oeis.org/A217318/b217318.txt", "Table"][[All, 2]];

a[n_] := (2 - Mod[n, 2]) A217318[[n]];

Array[a, 42] (* Jean-François Alcover, Sep 02 2019 *)

CROSSREFS

Cf. A000136, A000682, A077014.

Cf. A223093, A223094.

Sequence in context: A320526 A193519 A268329 * A052978 A151023 A344501

Adjacent sequences:  A223092 A223093 A223094 * A223096 A223097 A223098

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mar 29 2013

EXTENSIONS

Name clarified by Stéphane Legendre, Apr 09 2013

More terms from Stéphane Legendre, Apr 09 2013

STATUS

approved

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Last modified December 7 09:15 EST 2021. Contains 349574 sequences. (Running on oeis4.)