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A207851
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Number of meanders of order 2n+1 (4*n+2 crossings of the infinite line) with only central 1-1 cut (no other 1-1 cuts).
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2
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4, 16, 324, 12100, 595984, 35236096, 2363709924, 174221090404, 13815880848784, 1161868621405636, 102544273501721104, 9424551852935116804, 896612457556434503824, 87881363502264179831824, 8840846163309028336017124
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OFFSET
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1,1
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COMMENTS
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Central cut is a 1-1 cut at the center of the meander (the i-line is for i=n).
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REFERENCES
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A. Panayotopoulos and P. Tsikouras, Properties of meanders, JCMCC 46 (2003), 181-190.
A. Panayotopoulos and P. Vlamos, Meandric Polygons, Ars Combinatoria 87 (2008), 147-159.
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LINKS
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A. Panayotopoulos and P. Vlamos, Cutting Degree of Meanders, Artificial Intelligence Applications and Innovations, IFIP Advances in Information and Communication Technology, Volume 382, 2012, pp 480-489; DOI 10.1007/978-3-642-33412-2_49. - From N. J. A. Sloane, Dec 29 2012
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PROG
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(C/C++) int a(int n){
return w2(i)^2;
}
int w1(int order, int i){
if (i%2==0) error("error in w1(%d, %d), i is even\n", order, i);
if (order%2) error("error in w1(%d, %d), order is odd\n", order, i);
return w2(i+1)*w(order-i+1);
}
int w2(int order){
if (order%2) error("error in w2(%d), order is odd\n", order);
return w(order)-w3(order);
}
int w3(int order){
if (order%2) error("error in w3(%d), order is odd\n", order);
int sum=0;
int i;
for (i=3; i<=order-3; i+=2)
sum+=w1(order, i);
return sum;
}
// w(int i), no source here, is the respective meandric number according to Jensen A005315
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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