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A054791
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Earliest sequence with a(a(n))=n^2.
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2
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0, 1, 3, 4, 9, 6, 25, 8, 49, 16, 11, 100, 13, 144, 15, 196, 81, 18, 289, 20, 361, 22, 441, 24, 529, 36, 27, 676, 29, 784, 31, 900, 33, 1024, 35, 1156, 625, 38, 1369, 40, 1521, 42, 1681, 44, 1849, 46, 2025, 48, 2209, 64, 51, 2500, 53, 2704, 55, 2916, 57, 3136, 59
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OFFSET
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0,3
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
Index entries for sequences of the a(a(n)) = 2n family
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FORMULA
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if n is a square then a(n)=a(sqrt(n))^2, otherwise if the difference between n and the highest square less than n is odd then a(n)=n+1, otherwise a(n)=(n-1)^2
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MATHEMATICA
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a[n_] := a[n] = Which[r = Sqrt[n]; IntegerQ[r], a[r]^2, OddQ[n - Floor[r]^2], n+1, True, (n-1)^2]; a[0]=0; a[1]=1; Table[a[n], {n, 0, 58}] (* Jean-François Alcover, Aug 07 2012, after formula *)
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CROSSREFS
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Cf. A002516.
Sequence in context: A157020 A180253 A055225 * A167531 A062319 A178590
Adjacent sequences: A054788 A054789 A054790 * A054792 A054793 A054794
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KEYWORD
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nice,nonn
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AUTHOR
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Henry Bottomley, Apr 27 2000
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STATUS
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approved
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