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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
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
Sequence in context: A294736 A217427 A345339 * A242532 A132606 A054288
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 March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)