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Search: id:A120578
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| A120578 |
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Irregular array where the n-th row are the divisors, not occurring earlier in the sequence, of the sum of the terms in all previous rows. a(1)=4. |
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+0
4
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| 4, 1, 2, 7, 14, 28, 8, 56, 3, 5, 6, 10, 12, 15, 20, 24, 30, 40, 60, 120, 31, 93, 155, 465, 13, 39, 403, 1209, 17, 169, 221, 2873, 21, 293, 879, 2051, 6153, 25, 50, 311, 622, 1555, 3110, 7775, 15550, 37, 43, 74, 86, 148, 172, 259, 301, 518, 602, 1036, 1204, 1591
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Is this sequence a permutation of the positive integers?
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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Array begins:
4
1,2
7
14
28
8,56
Now these terms add up to 120. So row 7 is the divisors of 120 which do not occur earlier in the sequence. 1,2,4 and 8 occur in earlier rows, so row 7 is (3,5,6,10,12,15,20,24,30,40,60,120).
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MATHEMATICA
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f[t_] := Flatten[Append[t, Select[Divisors[Plus @@ t], FreeQ[t, # ] &]]]; Nest[f, {4}, 12] (*Chandler*)
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CROSSREFS
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Cf. A120576, A120577, A120579.
Sequence in context: A016685 A141332 A084460 this_sequence A096249 A081454 A133883
Adjacent sequences: A120575 A120576 A120577 this_sequence A120579 A120580 A120581
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KEYWORD
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nonn,tabf
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AUTHOR
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Leroy Quet Jun 15 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 17 2006
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