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A203777
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Aliquot sequence starting at 220.
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0
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220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284, 220, 284
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OFFSET
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0,1
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COMMENTS
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A period 2 sequence.
The sum of the proper divisors of 220 is 284 and the sum of the proper divisors of 284 is 220.
Sierpinski's book has typos for n = 1 and 3 (280 instead of 284).
Also continued fraction expansion of (7810+sqrt(61000005))/71. - Bruno Berselli, Jan 18 2012
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REFERENCES
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Waclaw Sierpinski: Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, p. 138.
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LINKS
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Table of n, a(n) for n=0..51.
Index to sequences with linear recurrences with constant coefficients, signature (0,1).
Wikipedia, Aliquot sequence
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FORMULA
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a(2*n) = 220, a(2*n+1) = 284.
a(n) = 4*(63-8*(-1)^n). - Paolo P. Lava, Jan 18 2012
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EXAMPLE
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a(0) = 220, a(1) = sigma(220) - 220 = 284.
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MATHEMATICA
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RecurrenceTable[{a[n] == DivisorSigma[1, a[n - 1]] - a[n - 1], a[0] == 220}, a, {n, 51}]
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CROSSREFS
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Cf. A063990.
Sequence in context: A157673 A064477 A217160 * A121507 A063990 A157107
Adjacent sequences: A203774 A203775 A203776 * A203778 A203779 A203780
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KEYWORD
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nonn,easy
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AUTHOR
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Arkadiusz Wesolowski, Jan 05 2012
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STATUS
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approved
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