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A100639
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Residues modulo 10 of the irregular primes (A000928).
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0
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7, 9, 7, 1, 3, 1, 9, 7, 3, 7, 3, 1, 3, 3, 7, 1, 7, 3, 9, 9, 1, 9, 1, 3, 1, 3, 7, 1, 3, 1, 7, 7, 7, 7, 3, 7, 3, 7, 9, 1, 7, 3, 9, 3, 7, 3, 1, 7, 1, 7, 1, 3, 7, 9, 1, 1, 7, 9, 7, 1, 7, 9, 3, 1, 1, 1, 7, 9, 1, 3, 3, 1, 7, 9, 7, 9, 3, 1, 7, 1, 7, 9, 7, 7, 1, 9, 9, 9, 3, 9, 3, 9, 7, 9, 3, 9, 1, 7, 3, 9, 1, 3, 3, 9, 7
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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REFERENCES
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Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, pp. 425-430 (but there are errors).
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LINKS
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EXAMPLE
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a(6) = 1 because the 6th irregular prime is 131.
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MATHEMATICA
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fQ[n_] := Block[{p = n, k = 1}, While[ 2*k <= p - 3 && Mod[ Numerator[ BernoulliB[ 2*k ]], p ] != 0, k++ ]; 2k != p - 1]; Mod[ Select[ Prime[ Range[2, 275]], fQ[ # ] &], 10] (* Robert G. Wilson v, Dec 10 2004 *)
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CROSSREFS
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KEYWORD
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easy,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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