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A098186 If f[x]=(sum of unitary-proper divisors of x)=A063919[x] is iterated, the iteration may lead to a fixed point which is either 0 or belongs to A002827, a unitary-perfect-number >1: 6,60,90,87360... Sequence gives initial values for which the iteration ends in 87360, the 4th unitary perfect number. 3
87360, 232608, 356640, 465144, 527712, 565728, 713208, 1018248, 1055352, 1211352, 1240032, 1303728, 1316904, 1352568, 1357584, 1360416, 1379280, 1550472, 1690440, 1835592, 2035608, 2078328, 2110632, 2262892, 2422632 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

Iteration list started from n=1018248: {1018248, 1055352, 527712, 232608, 87360, 87360...}

MATHEMATICA

di[x_] :=Divisors[x]; ta={{0}}; ud[x_] :=Part[di[x], Flatten[Position[GCD[di[x], Reverse[di[x]]], 1]]]; asu[x_] :=Apply[Plus, ud[x]]-x; nsf[x_, ho_] :=NestList[asu, x, ho] Do[g=n; s=Last[NestList[asu, n, 100]]; If[Equal[s, 87360], Print[{n, s}]; ta=Append[ta, n]], {n, 1, 5000000}]; ta = Delete[ta, 1]

CROSSREFS

Cf. A063919, A002827, A063991, A097024, A097030-A097037, A098185.

Sequence in context: A237410 A206632 A230489 * A069313 A022207 A251907

Adjacent sequences:  A098183 A098184 A098185 * A098187 A098188 A098189

KEYWORD

nonn

AUTHOR

Labos Elemer, Aug 31 2004

STATUS

approved

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Last modified June 21 00:57 EDT 2021. Contains 345329 sequences. (Running on oeis4.)