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A161577
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a(1)=2. a(n) = the smallest integer > a(n-1) such that d(a(n)) >= d(n), where d(n) = the number of divisors of n.
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3
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2, 3, 4, 6, 7, 8, 9, 10, 12, 14, 15, 18, 19, 20, 21, 24, 25, 28, 29, 30, 32, 33, 34, 36, 38, 39, 40, 42, 43, 48, 49, 50, 51, 52, 54, 60, 61, 62, 63, 66, 67, 70, 71, 72, 75, 76, 77, 80, 81, 84, 85, 88, 89, 90, 91, 96, 98, 99, 100, 108, 109, 110, 112, 114, 115, 120, 121, 124, 125
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OFFSET
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1,1
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COMMENTS
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Starting the sequence with a(1)=1 instead would have lead to a(n) = n for all n, obviously.
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LINKS
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MATHEMATICA
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nxt[{n_, a_}]:=Module[{k=a+1, d=DivisorSigma[0, n+1]}, While[DivisorSigma[0, k]<d, k++]; {n+1, k}]; NestList[nxt, {1, 2}, 80][[All, 2]] (* Harvey P. Dale, Aug 30 2017 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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