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A001989
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Class numbers associated with terms of A001988.
(Formerly M3756 N1535)
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0
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1, 1, 5, 7, 7, 7, 9, 53, 73, 83, 83, 83, 157, 185, 185, 185, 185, 1927, 2295, 2273, 5313, 5313, 7173, 9529, 18545, 18545, 18545, 18545, 22635, 22635, 66011, 121725, 344909, 344909
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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PROG
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(PARI) isok(p, oddpn) = {forprime(q=3, oddpn, if (kronecker(p, q) != -kronecker(-1, q), return (0)); ); return (1); }
a(n) = {my(oddpn = prime(n+1)); forprime(p=3, , if (((p%8) == 7) && isok(p, oddpn), return (qfbclassno(-p*if(p%4>1, 4, 1)))); ); } \\ Michel Marcus, Oct 19 2017
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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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