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A076618
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Least x>1 such that x^d == 1 (mod d) for each divisor d of n.
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2
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2, 3, 4, 3, 6, 7, 8, 3, 4, 11, 12, 7, 14, 15, 16, 3, 18, 7, 20, 11, 22, 23, 24, 7, 6, 27, 4, 15, 30, 31, 32, 3, 34, 35, 36, 7, 38, 39, 40, 11, 42, 43, 44, 23, 16, 47, 48, 7, 8, 11, 52, 27, 54, 7, 56, 15, 58, 59, 60, 31, 62, 63, 22, 3, 66, 67, 68, 35, 70, 71, 72, 7, 74, 75, 16, 39
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| If n is prime a(n)=n+1; for any k a(A000469(k))=A000469(k)+1; sum(k=1, n, a(k)) seems to be asymptotic to c*n^2 with c=0.35....
A076618(n) = SquareFreeKernel(n) + 1 = A007947(n) + 1. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 10 2004
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PROG
| (PARI) a(n)=if(n<0, 0, x=2; while(sumdiv(n, d, (x^d-1)%d)>0, x++); x)
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CROSSREFS
| Sequence in context: A074792 A048276 A127463 * A116550 A116991 A103634
Adjacent sequences: A076615 A076616 A076617 * A076619 A076620 A076621
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 22 2002
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