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 A203777 Aliquot sequence starting at 220. 0

%I

%S 220,284,220,284,220,284,220,284,220,284,220,284,220,284,220,284,220,

%T 284,220,284,220,284,220,284,220,284,220,284,220,284,220,284,220,284,

%U 220,284,220,284,220,284,220,284,220,284,220,284,220,284,220,284,220,284

%N Aliquot sequence starting at 220.

%C A period 2 sequence.

%C The sum of the proper divisors of 220 is 284 and the sum of the proper divisors of 284 is 220.

%C Sierpiński's book has typos for n = 1 and 3 (280 instead of 284).

%C Also continued fraction expansion of (7810+sqrt(61000005))/71. - _Bruno Berselli_, Jan 18 2012

%D Wacław Sierpiński, Czym sie zajmuje teoria liczb. Warsaw: PW "Wiedza Powszechna", 1957, p. 138.

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Aliquot_sequence">Aliquot sequence</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).

%F a(2*n) = 220, a(2*n+1) = 284.

%F a(n) = 4*(63-8*(-1)^n). - _Paolo P. Lava_, Jan 18 2012

%F a(n+1) = A001065(a(n)). - _R. J. Mathar_, Oct 11 2017

%e a(0) = 220, a(1) = sigma(220) - 220 = 284.

%t RecurrenceTable[{a[n] == DivisorSigma[1, a[n - 1]] - a[n - 1], a[0] == 220}, a, {n, 51}]

%Y Cf. A063990.

%K nonn,easy

%O 0,1

%A _Arkadiusz Wesolowski_, Jan 05 2012

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Last modified July 21 17:20 EDT 2019. Contains 325198 sequences. (Running on oeis4.)