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Search: id:A120577
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| A120577 |
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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)=3. |
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+0
4
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| 3, 1, 2, 4, 5, 10, 25, 50, 20, 100, 11, 22, 44, 55, 110, 220, 31, 62, 341, 682, 29, 58, 899, 1798, 79, 158, 2291, 4582, 37, 74, 148, 316, 2923, 5846, 11692, 8, 4091, 8182, 16364, 32728, 7, 21, 4481, 13443, 31367, 94101, 23, 449, 529, 10327, 237521, 17, 34, 85, 170
(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:
3
1
2,4
5,10
25
50
Now these terms add up to 100. So row 7 is the divisors of 100 which do not occur earlier in the sequence. 1,2,4,5,10,25 and 50 occur in earlier rows, so row 7 is (20,100).
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MATHEMATICA
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f[t_] := Flatten[Append[t, Select[Divisors[Plus @@ t], FreeQ[t, # ] &]]]; Nest[f, {3}, 15] (*Chandler*)
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CROSSREFS
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Cf. A120576, A120578, A120579.
Sequence in context: A074585 A108038 A151845 this_sequence A104695 A083275 A138382
Adjacent sequences: A120574 A120575 A120576 this_sequence A120578 A120579 A120580
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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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