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1, 2, 8, 19, 56, 147, 404, 1082, 2954, 8001, 21865, 59759, 164085, 451465, 1246358, 3448876, 9569376, 26611517, 74172493, 207159274, 579724677, 1625287220, 4564461309, 12839597611, 36172421770, 102053738981, 288317817804
(list; graph; refs; listen; history; internal format)
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OFFSET
| 4,2
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COMMENTS
| Counts exceptional non-overlapping circles. These circles are exceptional because they are neither generated by encircling any case at level n-1 nor do they result from appending an external circle to any case at level n-1. When n=4 the case is (())(()).
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EXAMPLE
| a(8) = 56 because we can write A000081(9) - 2*(A000081(8)= 286 - 2*115 a(8) also = 56 because we know that 8=6+2=5+3=4+4=4+2+2=3+3+2=2+2+2+2 and these partitions contribute 20*1 + 9*2 + 4*5/2 + 4 + 3 + 1 cases.
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CROSSREFS
| Sequence in context: A107769 A026588 A026572 * A129445 A082821 A188893
Adjacent sequences: A074794 A074795 A074796 * A074798 A074799 A074800
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KEYWORD
| easy,nonn
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AUTHOR
| Alford Arnold (Alford1940(AT)aol.com), Sep 07 2002
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EXTENSIONS
| More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Feb 10 2003
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