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A123088
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a(1)=1. For n>=2, a(n) = n + (largest integer which is <= n and is missing from the earlier terms of the sequence).
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2
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1, 4, 6, 7, 10, 11, 12, 16, 18, 19, 20, 21, 26, 28, 30, 31, 34, 35, 36, 37, 38, 44, 46, 48, 50, 51, 54, 55, 58, 59, 60, 64, 66, 67, 68, 69, 70, 71, 78, 80, 82, 84, 86, 87, 90, 91, 94, 95, 98, 99, 100, 104, 106, 107, 108, 112, 114, 115, 116, 117, 122, 124, 126, 127, 130, 131
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| The largest integer which is <= 12 and does not occur among the first 11 terms of the sequence is 9. So a(12) = 12 + 9 = 21.
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MATHEMATICA
| f[l_List] := Block[{n = Length[l] + 1, k = n}, While[MemberQ[l, k], k-- ]; Append[l, n + k]]; Nest[f, {1}, 70] (*Chandler*)
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PROG
| (PARI) {m=66; w=vector(2*m); print1(a=1, ", "); for(n=2, m, k=n; while(w[k], k--); print1(a=n+k, ", "); w[a]=1)} - (Klaus Brockhaus, Oct 05 2006)
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CROSSREFS
| Cf. A123679.
Sequence in context: A010418 A087790 A086170 * A189085 A153235 A133483
Adjacent sequences: A123085 A123086 A123087 * A123089 A123090 A123091
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Sep 27 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 30 2006
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