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Search: id:A075392
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| A075392 |
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a(1) = 1, then the smallest nontrivial k (>1) which divides the sum of (next n) numbers from k+1 to k+n or smallest k > 1 that divides nk + n(n+1)/2. |
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1
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| 1, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 7, 3, 2, 2, 3, 3, 2, 2, 3, 11, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 19, 3, 2, 2, 3, 3, 2, 2, 3, 23, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 29, 2, 2, 31, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 37, 3, 2, 2, 3, 3, 2, 2, 3, 41, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 7, 3, 2
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(4n) = 2.
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EXAMPLE
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a(7) = 4, which is the smallest nontrivial number that divides the sum 5+6+...+11, of 7 numbers.
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PROGRAM
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(PARI) for(n=2, 120, for(k=2, 10^9, if((n*k+n*(n+1)/2)%k==0, print1(k", "):break)))
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CROSSREFS
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Sequence in context: A049234 A125504 A069901 this_sequence A115039 A032536 A115061
Adjacent sequences: A075389 A075390 A075391 this_sequence A075393 A075394 A075395
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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), Sep 22 2002
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EXTENSIONS
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Corrected and extended by Ralf Stephan (ralf(AT)ark.in-berlin.de), Mar 27 2003
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