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Search: id:A104512
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| A104512 |
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Minimum number a(n) which is the first of k>1 consecutive integers, the sum of which equals n, or 0 if impossible. |
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+0
5
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| 0, 0, 1, 0, 2, 1, 3, 0, 2, 1, 5, 3, 6, 2, 1, 0, 8, 3, 9, 2, 1, 4, 11, 7, 3, 5, 2, 1, 14, 4, 15, 0, 3, 7, 2, 1, 18, 8, 4, 6, 20, 3, 21, 2, 1, 10, 23, 15, 4, 8, 6, 3, 26, 2, 1, 5, 7, 13, 29, 4, 30, 14, 3, 0, 2, 1, 33, 5, 9, 7, 35, 4, 36, 17, 3, 6, 2, 1, 39, 14, 5, 19, 41, 7, 4, 20, 12, 3, 44, 2, 1, 8, 13
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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a(n)=0 iff n=2^k and a(n)=1 iff n is a triangular number (A000217).
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REFERENCES
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Alfred S. Posamentier, Math Charmers, Tantalizing Tidbits for the Mind, Prometheus Books, NY, 2003, page 67.
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EXAMPLE
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a(18) = 3 because 3+4+5+6 = 5+6+7 = 18 but 3 < 5.
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MATHEMATICA
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f[n_] := Block[{r = Ceiling[n/2]}, If[ IntegerQ[ Log[2, n]], 0, m = Range[r]; lst = Flatten[ Table[ m[[k]], {i, r}, {j, i + 1, r}, {k, i, j}], 1]; lst[[ Position[ Plus @@@ lst, n, 1, 1][[1, 1]], 1]]]]; Table[ f[n], {n, 93}] (from Robert G. Wilson v Feb 25 2005)
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CROSSREFS
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Cf. A104513, A104514, A104515, A104516.
Sequence in context: A125073 A071461 A091829 this_sequence A131848 A035157 A087469
Adjacent sequences: A104509 A104510 A104511 this_sequence A104513 A104514 A104515
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KEYWORD
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nonn
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AUTHOR
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Alfred S. Posamentier (asp2(AT)juno.com) and Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 23 2005
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