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Search: id:A019444
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| A019444 |
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a_1, a_2, ..., is a permutation of the positive integers such that the average of each initial segment is an integer, using the greedy algorithm to define a_n. |
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+0
6
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| 1, 3, 2, 6, 8, 4, 11, 5, 14, 16, 7, 19, 21, 9, 24, 10, 27, 29, 12, 32, 13, 35, 37, 15, 40, 42, 17, 45, 18, 48, 50, 20, 53, 55, 22, 58, 23, 61, 63, 25, 66, 26, 69, 71, 28, 74, 76, 30, 79, 31, 82, 84, 33, 87, 34, 90, 92, 36, 95, 97, 38, 100, 39, 103, 105, 41, 108, 110, 43, 113
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Self-inverse when considered as a permutation or function, i.e. a(a(n)) = n. - Howard A. Landman (howard(AT)polyamory.org), Sep 25 2001
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LINKS
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Problem of the week, Web site - problem 818
Index entries for sequences that are permutations of the natural numbers
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MATHEMATICA
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a[1]=1; a[n_] := a[n]=Module[{s, v}, s=a/@Range[n-1]; For[v=Mod[ -Plus@@s, n], v<1||MemberQ[s, v], v+=n, Null]; v]
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CROSSREFS
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Cf. A019445, A019446. A019444 = A002251 + 1.
Sequence in context: A021310 A127717 A120232 this_sequence A069773 A122321 A072093
Adjacent sequences: A019441 A019442 A019443 this_sequence A019445 A019446 A019447
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KEYWORD
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nonn
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AUTHOR
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R. K. Guy and Tom Halverson (halverson(AT)macalester.edu)
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