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A165442 Start with m, repeatedly find sum of prime factors until we reach a fixed point, then compute sum of numbers in trajectory except for m and the fixed point. If the resulting sum equals m, adjoin m to the sequence. 0
20, 38, 74 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No further terms below 10^13. Note that if the sum of the prime factors of a composite number equals itself, then it can only be 4.

LINKS

Table of n, a(n) for n=1..3.

EXAMPLE

Take 20 as example, the sum of its prime factors is 9, then we move on until we get a prime, 9=3x3, 3+3=6, and 6=2x3, 2+3=5, add all the results in the process, 9+6+5=20. 20=9+6+5, 38=21+10+7, 74=39+16+8+6+5.

CROSSREFS

Cf. A001414, A029908.

Sequence in context: A259734 A294736 A217427 * A242532 A132606 A054288

Adjacent sequences:  A165439 A165440 A165441 * A165443 A165444 A165445

KEYWORD

nonn,more,bref

AUTHOR

K. T. Lee (7x3(AT)21cn.com), Sep 19 2009

EXTENSIONS

Edited by N. J. A. Sloane, Sep 20 2009

STATUS

approved

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Last modified February 27 15:16 EST 2020. Contains 332307 sequences. (Running on oeis4.)