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A151998
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Directed genus of the binary de Bruijn graph D_n.
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0
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0, 0, 0, 1, 2, 7, 15, 35, 75, 163, 337, 709, 1458, 3001, 6135, 12529, 25468, 51739, 104829, 212205, 428916, 866215, 1747527, 3523213, 7097895, 14291683, 28760643, 57852469, 116321445, 233798623, 469761015, 943591237, 1894836585, 3804113881, 7635493643
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,5
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LINKS
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FORMULA
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See Maple code.
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MAPLE
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with(numtheory);
f:=proc(n) local t1, t2, t3, i;
t1:=divisors(n+2); t2:=convert(t1, list);
t3:=add( phi(t2[i])*2^((n+2)/t2[i]), i =1..nops(t2));
2^(n-1) + 1 - t3/(2*(n+2));
end;
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PROG
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(PARI) a(n) = 2^(n-1) + 1 - sumdiv(n+2, d, 2^((n+2)/d)*eulerphi(d))/(2*(n+2)); \\ Michel Marcus, Mar 02 2019
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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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