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 A203777 Aliquot sequence starting at 220. 0
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS 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. Sierpiński'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 REFERENCES Wacław Sierpiński, Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, p. 138. LINKS Wikipedia, Aliquot sequence Index entries for linear recurrences with constant coefficients, signature (0,1). FORMULA a(2*n) = 220, a(2*n+1) = 284. a(n) = 4*(63-8*(-1)^n). - Paolo P. Lava, Jan 18 2012 a(n+1) = A001065(a(n)). - R. J. Mathar, Oct 11 2017 EXAMPLE a(0) = 220, a(1) = sigma(220) - 220 = 284. MATHEMATICA RecurrenceTable[{a[n] == DivisorSigma[1, a[n - 1]] - a[n - 1], a[0] == 220}, a, {n, 51}] CROSSREFS Cf. A063990. Sequence in context: A157673 A064477 A217160 * A274116 A121507 A255215 Adjacent sequences:  A203774 A203775 A203776 * A203778 A203779 A203780 KEYWORD nonn,easy AUTHOR Arkadiusz Wesolowski, Jan 05 2012 STATUS approved

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)