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A248528
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Numbers n such that the smallest prime divisor of n^2+1 is 17.
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5
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4, 30, 64, 106, 140, 166, 234, 276, 310, 336, 344, 370, 404, 446, 480, 506, 514, 540, 574, 650, 676, 744, 786, 820, 846, 854, 880, 914, 956, 990, 1016, 1024, 1050, 1160, 1186, 1194, 1220, 1254, 1296, 1330, 1356, 1364, 1390, 1424, 1466, 1534, 1560, 1636, 1670
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OFFSET
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1,1
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COMMENTS
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Or numbers n such that the smallest prime divisor of n^2+1 is A002313(4).
a(n)== 4 or 30 (mod 34).
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LINKS
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EXAMPLE
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30 is in the sequence because 30^2+1= 17*53.
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MATHEMATICA
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lst={}; Do[If[FactorInteger[n^2+1][[1, 1]]==17, AppendTo[lst, n]], {n, 2, 2000}]; lst
p = 17; ps = Select[Range[p - 1], Mod[#, 4] != 3 && PrimeQ[#] &]; Select[Range[1670], Divisible[(nn = #^2 + 1), p] && ! Or @@ Divisible[nn, ps] &] (* Amiram Eldar, Aug 16 2019 *)
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PROG
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(Magma) [n: n in [2..2000] | PrimeDivisors(n^2+1)[1] eq 17]; // Bruno Berselli, Oct 08 2014
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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