

A001989


Class numbers associated with entries of A001988.
(Formerly M3756 N1535)


0



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
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OFFSET

1,3


REFERENCES

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).


LINKS

Table of n, a(n) for n=1..34.
D. H. Lehmer, E. Lehmer and D. Shanks, Integer sequences having prescribed quadratic character, Math. Comp., 24 (1970), 433451.
D. H. Lehmer, E. Lehmer and D. Shanks, Integer sequences having prescribed quadratic character, Math. Comp., 24 (1970), 433451 [Annotated scanned copy]


PROG

(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


CROSSREFS

Cf. A001988.
Sequence in context: A093723 A065773 A114916 * A086056 A154475 A264527
Adjacent sequences: A001986 A001987 A001988 * A001990 A001991 A001992


KEYWORD

nonn


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Better name from Sean A. Irvine, Mar 06 2013
Terms corrected by Sean A. Irvine, Mar 06 2013
Offset changed by Michel Marcus, Oct 19 2017


STATUS

approved



