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Search: id:A093313
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| A093313 |
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Number of permutations s_1,s_2,...,s_n of 1,2,...,n with s_1 = 2 and such that for all j=1,2,...,n, s_j divides Sum_{i=1..j} s_i. |
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4
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| 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 6, 1, 11, 9, 15, 14, 14, 23
(list; graph; listen)
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OFFSET
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1,36
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COMMENT
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An easy calculation turns out that the beginning elements are always: 2,1,3,6,(then either 4 or 12),...
The total number of permutations with this property is given in A067957.
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REFERENCES
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Matthijs Coster, Problem 2001/3-A of the Universitaire Wiskunde Competitie, Nieuw Arch. Wisk. 5/3 (2002), 92-94.
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LINKS
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Matthijs Coster, Sequences
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EXAMPLE
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There is a unique permutation of the numbers 1..38, starting with 2, namely:
2 1 3 6 12 24 8 28 21 35 14 22 4 20 25 5 23 11 33 27 9 37 10 19 7 29 15 30 16 31 17 32 36 34 38 18 26 13
with corresponding sums
2 3 6 12 24 48 56 84 105 140 154 176 180 200 225 230 253 264 297 324 333 370 380 399 406 435 450 480 496 527 544 576 612 646 684 702 728 741.
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CROSSREFS
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Cf. A067957, A093314, A093315.
Sequence in context: A073012 A102522 A105817 this_sequence A098267 A122193 A098369
Adjacent sequences: A093310 A093311 A093312 this_sequence A093314 A093315 A093316
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KEYWORD
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nonn
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AUTHOR
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Matthijs Coster (matthijs(AT)coster.demon.nl), Apr 26 2004; revised Aug 05 2005
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