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Search: id:A140611
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| A140611 |
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Consecutive N at which the prime running totals of prime factors in composites are found. |
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+0
2
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| 4, 6, 10, 15, 16, 24, 26, 32, 42, 72, 78, 81, 102, 111, 124, 168, 172, 182, 196, 205, 209, 212, 240, 243, 276, 299, 301, 308, 320, 326, 345, 357, 361, 412, 425, 426, 427, 429, 455, 477, 490, 494, 526, 564, 591, 605, 610, 637, 638, 645, 664, 670, 672, 682, 684
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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Compute prime factors (without multiplicity) of consecutive composite N. Maintain a running sum of these prime factors. Whenever the running total at N is prime, add to the sequence.
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EXAMPLE
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a(2)=6 because when N=6 the sum of composite prime factors is 7 and this total is prime (nonprime totals are not in this sequence). The prime factor (without multiplicity) of the first composite 4 is 2; the second composite is 6 with prime factors 3 and 2, so 2+2+3=7, the prime sum of prime factors at N=6.
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CROSSREFS
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Cf. A140610.
Sequence in context: A000066 A061645 A084372 this_sequence A076957 A121214 A116996
Adjacent sequences: A140608 A140609 A140610 this_sequence A140612 A140613 A140614
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KEYWORD
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easy,nonn
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), May 19 2008
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