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A115118 Number of imprimitive (periodic) n-bead binary necklaces with beads of 2 colors where the colors may be swapped but turning over is not allowed. 2
0, 0, 1, 1, 2, 1, 3, 1, 4, 2, 5, 1, 10, 1, 11, 5, 20, 1, 36, 1, 58, 11, 95, 1, 196, 4, 317, 30, 598, 1, 1153, 1, 2068, 95, 3857, 13 (list; graph; refs; listen; history; internal format)
OFFSET

0,5

COMMENTS

a(p)=1 for prime p. Presumably a(n)=A115121(n)=A066656(n)/2 for odd n.

FORMULA

a(n)=A000013(n) - A000048(n).

CROSSREFS

Sequence in context: A064576 A113308 A143862 * A115121 A124072 A189357

Adjacent sequences:  A115115 A115116 A115117 * A115119 A115120 A115121

KEYWORD

easy,nonn

AUTHOR

Valery A. Liskovets (liskov(AT)im.bas-net.by), Jan 17 2006

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Last modified February 18 00:14 EST 2012. Contains 206085 sequences.