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A120576
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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)=2.
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3
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2, 1, 3, 6, 4, 12, 7, 14, 28, 11, 77, 5, 15, 33, 55, 165, 73, 146, 219, 438, 9, 18, 657, 1314, 8, 16, 23, 24, 36, 46, 48, 69, 72, 92, 138, 144, 184, 207, 276, 368, 414, 552, 828, 1104, 1656, 3312, 1847, 12929, 5541, 9235, 27705, 19, 38, 3694, 35093, 70186, 487, 974
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Is this sequence a permutation of the positive integers?
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EXAMPLE
| Array begins:
2
1
3
6
4,12
7,14,28
Now these terms add up to 77. So row 7 is the divisors of 77 which do not occur earlier in the sequence. 1 and 7 occur in earlier rows, so row 7 is (11,77).
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MATHEMATICA
| f[t_] := Flatten[Append[t, Select[Divisors[Plus @@ t], FreeQ[t, # ] &]]]; Nest[f, {2}, 14] (*Chandler*)
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CROSSREFS
| Cf. A120577, A120578, A120579.
Sequence in context: A193897 A133904 A094339 * A063707 A205840 A171084
Adjacent sequences: A120573 A120574 A120575 * A120577 A120578 A120579
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KEYWORD
| nonn,tabf
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AUTHOR
| Leroy Quet Jun 15 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 17 2006
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