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Search: id:A020902
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| A020902 |
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Number of nonisomorphic cyclic subgroups of alternating group A_n (or number of distinct orders of even permutations of n objects); number of different lcm's of partitions of n which have even number of even parts. |
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+0
3
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| 1, 1, 1, 2, 3, 4, 5, 7, 8, 11, 13, 16, 18, 22, 26, 30, 35, 39, 46, 51, 60, 67, 76, 84, 94, 105, 119, 133, 147, 162, 176, 196, 218, 240, 263, 286, 310, 340, 374, 409, 441, 476, 515, 559, 608, 662, 711, 762, 817, 883, 955, 1030, 1104, 1177, 1257, 1352, 1453, 1559
(list; graph; listen)
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OFFSET
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0,4
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REFERENCES
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V. Jovovic, Some combinatorial characteristics of symmetric and alternating groups (in Russian), Belgrade, 1980, unpublished.
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FORMULA
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a(n)=A009490(n-2)+A035942(n-1)+A035942(n), n>1, a(0)=a(1)=1.
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EXAMPLE
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a(8)=8 because lcm{1^8}=1,lcm{1^4 2^2,2^4}=2,lcm{1^5 3^1,1^2 3^2}=3,lcm{4^2,1^2 2^1 4^1}=4,lcm{1^3 5^1}=5,lcm{2^1 6^1,1^1 2^2 3^1}=6,lcm{1^1 7^1}=7,lcm{3^1 5^1}=15.
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CROSSREFS
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Cf. A034891.
Sequence in context: A090467 A053868 A081730 this_sequence A008751 A029002 A031121
Adjacent sequences: A020899 A020900 A020901 this_sequence A020903 A020904 A020905
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu)
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