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A225508
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-4-Knödel numbers.
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9
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4, 6, 8, 12, 14, 16, 20, 24, 40, 48, 56, 60, 66, 80, 104, 120, 140, 176, 204, 240, 260, 266, 476, 560, 696, 728, 920, 1020, 1040, 1292, 1508, 1634, 1736, 1820, 1976, 2320, 2544, 2660, 3416, 3440, 3848, 4136, 4686, 4756, 5180, 5456, 6188, 6608, 7280, 8004, 8816
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OFFSET
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1,1
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COMMENTS
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Extension of k-Knödel numbers to k negative, in this case equal to -4. Composite numbers n > 0 such that if 1 < a < n and gcd(n,a) = 1 then a^(n+4) = 1 mod n.
All terms are even numbers.
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LINKS
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MAPLE
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with(numtheory); ListA225508:=proc(q, k) local a, n, ok;
for n from 2 to q do if not isprime(n) then ok:=1; for a from 1 to n do
if gcd(a, n)=1 then if (a^(n-k)-1) mod n<>0 then ok:=0; break; fi; fi;
od; if ok=1 then print(n); fi; fi; od; end: ListA225508(10^6, -4);
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MATHEMATICA
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Select[Range[10000], CompositeQ[#] && Divisible[# + 4, CarmichaelLambda[#]] &] (* Amiram Eldar, Mar 28 2019 *)
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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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