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A223093 Number of foldings of n labeled stamps in which leaf 1 is inwards and leaf n outwards (or leaf 1 outwards and leaf n inwards). 3
0, 0, 2, 4, 16, 38, 132, 342, 1144, 3134, 10370, 29526, 97458, 285458, 942920, 2822310, 9341008, 28440970, 94358558, 291294678, 968853072, 3025232480, 10086634316, 31797822936, 106265437078, 337731551446, 1131117792978, 3620119437762, 12148796744234, 39118879440938 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

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) = A000682(n+1) - A077014(n). - Andrew Howroyd, Dec 06 2015

A217310(n) = 2*a(n) if n is odd and A217310(n) = a(n) if n is even. - Stéphane Legendre, Jan 09 2014

MATHEMATICA

A000682 = Cases[Import["https://oeis.org/A000682/b000682.txt", "Table"], {_, _}][[All, 2]];

A077014 = Cases[Import["https://oeis.org/A077014/b077014.txt", "Table"], {_, _}][[All, 2]];

a[n_] := A000682[[n + 1]] - A077014[[n + 1]];

Array[a, 30] (* Jean-François Alcover, Sep 07 2019, after Andrew Howroyd *)

CROSSREFS

Sequence in context: A051861 A296297 A290265 * A333022 A048222 A192890

Adjacent sequences:  A223090 A223091 A223092 * A223094 A223095 A223096

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 July 27 18:27 EDT 2021. Contains 346308 sequences. (Running on oeis4.)