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A053674
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Least number coprime to n, n+1, n+2, n+3, n+4 and n+5.
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13
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7, 11, 11, 11, 11, 13, 13, 7, 17, 17, 17, 11, 11, 11, 7, 11, 13, 13, 13, 13, 17, 7, 11, 11, 11, 11, 11, 13, 7, 13, 13, 13, 13, 11, 11, 7, 11, 11, 17, 13, 13, 13, 7, 13, 11, 11, 11, 11, 11, 7, 19, 17, 13, 13, 13, 11, 7, 11, 11, 11, 17, 17, 19, 7, 19, 13, 11, 11, 11, 11, 7, 13
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OFFSET
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1,1
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COMMENTS
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All terms are primes greater than 5. Records: a(1) = 7, a(2) = 11, a(6) = 13, a(9) = 17, a(51) = 19, a(151) = 23, a(437) = 29, a(779) = 31, a(1766) = 37, a(60605) = 41, a(324596) = 43, a(3555107) = 47, a(14511250) = 53, a(65209022) = 59, a(764050703) = 61, .... - Charles R Greathouse IV, Feb 07 2017
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LINKS
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MATHEMATICA
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a[n_] := (k = 7; While[ ! And @@ (CoprimeQ[k, #] & ) /@ Range[n, n+5], k++]; k); Table[a[n], {n, 1, 72}] (* Jean-François Alcover, Nov 30 2011 *)
cpr[n_]:=Module[{k=7}, While[Union[Boole[CoprimeQ[k, n+Range[0, 5]]]]!={1}, k = NextPrime[ k]]; k](* Harvey P. Dale, May 12 2022 *)
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PROG
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(Haskell)
import Data.List (elemIndex)
import Data.Maybe (fromJust)
a053674 n = 2 + fromJust
(elemIndex 1 $ map (gcd $ foldl1 lcm $ take 6 [n..]) [2..])
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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EXTENSIONS
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More terms from Andrew Gacek (andrew(AT)dgi.net), Feb 21 2000 and James A. Sellers, Feb 22 2000
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STATUS
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approved
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