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A100764
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a(1) = 1, a(2) = 2, a(3) = 3, a(n) = least number not the sum of three or less previous terms.
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0
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1, 2, 3, 7, 13, 19, 25, 31, 37, 43, 49, 55, 61, 67, 73, 79, 85, 91, 97, 103, 109, 115, 121, 127, 133, 139, 145, 151, 157, 163, 169, 175, 181, 187, 193, 199, 205, 211, 217, 223, 229, 235, 241, 247, 253, 259, 265, 271, 277, 283, 289, 295, 301, 307, 313, 319, 325
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Generalization: let the first k terms of the sequence be 1,2,...k. and a(n), n > k be defined, as the least positive integer, not the sum of k or less previous terms then a(n+k) = a(n) + n* k(k+1)/2. a(n) = (n+1)*k*(k+1)/2 + 1. n > k.
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FORMULA
| a(n+4) = a(4) + 6n for n > 4; a(n) = 6n - 17, n >3.
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MATHEMATICA
| a[1] = 1; a[2] = 2; a[3] = 3; a[n_] := a[n] = (m = 1; l = n - 1; t = Union[ Flatten[ Join[ Table[ a[i], {i, l}], Table[ a[i] + a[j], {i, l}, {j, i + 1, l}], Table[ a[i] + a[j] + a[k], {i, l}, {j, i + 1, l}, {k, j + 1, l}] ]]]; While[ Position[t, m] != {}, m++ ]; m); Table[ a[n], {n, 60}] (from Robert G. Wilson v Dec 14 2004)
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CROSSREFS
| Essentially the same as A016921.
Sequence in context: A105792 A130903 A068828 * A076974 A051484 A101415
Adjacent sequences: A100761 A100762 A100763 * A100765 A100766 A100767
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KEYWORD
| easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 25 2004
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 14 2004
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