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A016726
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Smallest k such that 1, 4, 9, ..., n^2 are distinct mod k.
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3
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1, 2, 6, 9, 10, 13, 14, 17, 19, 22, 22, 26, 26, 29, 31, 34, 34, 37, 38, 41, 43, 46, 46, 53, 53, 53, 58, 58, 58, 61, 62, 67, 67, 71, 71, 73, 74, 79, 79, 82, 82, 86, 86, 89, 94, 94, 94, 97, 101, 101, 103, 106, 106, 109, 113, 113, 118, 118, 118, 122, 122, 127, 127, 131, 131, 134
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
Arnold, L. K.; Benkoski, S. J.; and McCabe, B. J.; The discriminator (a simple application of Bertrand's postulate). Amer. Math. Monthly 92 (1985), 275-277.
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FORMULA
| For n > 4, a(n) is smallest k >= 2n such that k = p or k = 2p, p a prime.
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MATHEMATICA
| a[n_] := (k = 2n; While[ Not[PrimeQ[k] || PrimeQ[k/2]], k++]; k); a[1]=1; a[2]=2; a[3]=6; a[4]=9; Table[a[n], {n, 1, 66}] (* From Jean-François Alcover, Nov 30 2011, after formula *)
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PROG
| (Haskell)
a016726 n = a016726_list !! (n-1)
a016726_list = [1, 2, 6, 9] ++ (f 5 $ drop 4 a001751_list) where
f n qs'@(q:qs) | q < 2*n = f n qs
| otherwise = q : f (n+1) qs'
-- Reinhard Zumkeller, Jun 20 2011
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CROSSREFS
| Cf. A001751.
Sequence in context: A198230 A121248 A108370 * A047396 A085304 A015843
Adjacent sequences: A016723 A016724 A016725 * A016727 A016728 A016729
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KEYWORD
| nonn,nice
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AUTHOR
| bernie(AT)wagnerpa.com (Bernie McCabe)
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