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Search: id:A061228
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| A061228 |
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a(1) = 2, a(n) = smallest number greater than n which is not coprime to n. |
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+0
2
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| 2, 4, 6, 6, 10, 8, 14, 10, 12, 12, 22, 14, 26, 16, 18, 18, 34, 20, 38, 22, 24, 24, 46, 26, 30, 28, 30, 30, 58, 32, 62, 34, 36, 36, 40, 38, 74, 40, 42, 42, 82, 44, 86, 46, 48, 48, 94, 50, 56, 52, 54, 54, 106, 56, 60, 58, 60, 60, 118, 62, 122, 64, 66, 66, 70, 68, 134, 70, 72, 72
(list; graph; listen)
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OFFSET
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0,1
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FORMULA
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a(2m) = 2m+2, a(p)= 2p if p is a prime.
a(n)= n + the smallest divisor (more than 1) of n.
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EXAMPLE
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a(9) = 12 as 10 and 11 are coprime to 9. a(11) = 22. as 11 is a prime.
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MAPLE
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for n from 1 to 150 do if n=1 then printf(`%d, `, 2); fi: for k from n+1 to 2*n do if igcd(n, k)>1 then printf(`%d, `, k); break; fi: od: od:
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CROSSREFS
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A020639(n+1) + n.
Sequence in context: A049066 A056942 A115947 this_sequence A070229 A053568 A037225
Adjacent sequences: A061225 A061226 A061227 this_sequence A061229 A061230 A061231
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 23 2001
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Apr 24 2001
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