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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

Table of n, a(n) for n=0..51.

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.)