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A135590
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Numbers k such that k^2 + 1 is a Sarrus number (pseudoprime to base 2).
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4
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216, 948, 1560, 4872, 8208, 9828, 18200, 29640, 37024, 65536, 89550, 283800, 535920, 592956, 649800, 825930, 1042320, 1382400, 1536220, 3688230, 4215120, 4321800, 5103210, 19078930, 21415680, 24471720, 214067490, 435457620, 535019100
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OFFSET
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1,1
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COMMENTS
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Note that A000215(5) corresponds to a(10), and A000215(6) corresponds to a(33), and in general when A000215(n) is composite, this sequence has corresponding entry. - Jeppe Stig Nielsen, Mar 26 2016
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LINKS
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MATHEMATICA
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fQ[n_] := ( !PrimeQ[n^2 + 1] && PowerMod[2, n^2, n^2 + 1] == 1); lst = {}; Do[ If[ fQ@ n, AppendTo[lst, n]], {n, 2, 440000000, 2}]; lst (* Robert G. Wilson v, Apr 18 2008 *)
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PROG
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(PARI) is(n) = {Mod(2, n)^(n-1)==1 && !ispseudoprime(n) && n > 1};
for(n=1, 1e10, if(is(n^2+1), print1(n, ", "))); \\ Altug Alkan, Mar 26 2016
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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