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Search: id:A018845
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| A018845 |
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Number of iterations required for the sum of n and its prime divisors = t to reach a prime (where t replaces n in each iteration) in A016837. |
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+0
2
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| 1, 4, 2, 3, 2, 1, 2, 2, 2, 1, 3, 1, 2, 1, 1, 3, 2, 2, 2, 1, 1, 2, 2, 2, 2, 1, 3, 3, 2, 3, 5, 4, 1, 1, 1, 2, 2, 1, 2, 2, 10, 3, 2, 1, 6, 1, 3, 1, 5, 5, 1, 5, 3, 2, 1, 2, 4, 2, 2, 4, 3, 4, 3, 4, 13, 13, 3, 4, 3, 4, 3, 3, 3, 4, 12
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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Factor n, add n and its prime divisors. Sum = t, t replaces n, repeat until a prime is produced in k iterations.
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EXAMPLE
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a(4)=4. 4=2*2, so 4+2+2=8. 8=2*2*2 so 8+2+2+2=14. 14=2*7 so 14+2+7=23, prime in 3 iterations.
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CROSSREFS
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Sequence in context: A134977 A016513 A063447 this_sequence A028947 A068152 A079636
Adjacent sequences: A018842 A018843 A018844 this_sequence A018846 A018847 A018848
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KEYWORD
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easy,nonn
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AUTHOR
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Enoch Haga, Carlos B. Rivera F., Patrick De Geest (Enokh(AT)comcast.net, crivera(AT)ux1.sci.net.mx, pdg(AT)worldofnumbers.com)
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