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A191408 Duplicate of A006641. 4
1, 1, 1, 1, 1, 2, 1, 2, 3, 2, 3, 2, 4, 2, 1, 5, 2, 2, 4, 4, 3, 1, 4, 7, 5, 3, 4, 6, 2, 2, 8, 5, 6, 3, 8, 2, 6, 10, 4, 2, 5, 5, 4, 4, 3, 10, 2, 7, 6, 4, 10, 1, 8, 11, 4, 5, 8, 4, 2, 13, 4, 9, 4, 3, 6, 14, 4, 7, 5, 4, 12, 2, 2, 15, 6, 6, 8, 7, 12, 4, 8, 13, 8, 2, 11, 8, 4, 3, 14, 4, 4, 8, 10, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Same as A006641. - Georg Fischer, Oct 12 2018

LINKS

Table of n, a(n) for n=1..94.

FORMULA

Class number of A003657(n).

MATHEMATICA

FundamentalDiscriminantQ[n_Integer] := n != 1 && (Mod[n, 4] == 1 || !Unequal[ Mod[n, 16], 8, 12]) && SquareFreeQ[n/2^IntegerExponent[n, 2]] (* via Eric W. Weisstein *);

NumberFieldClassNumber@ Sqrt@ # & /@ Select[-Range@ 300, FundamentalDiscriminantQ]

PROG

(PARI) for(n=1, 300, if(isfundamental(-n), print1(quadclassunit(-n).no, ", "))) \\ Andrew Howroyd, Jul 23 2018

CROSSREFS

Cf. A191410.

Sequence in context: A012265 A268835 A006641 * A115756 A067731 A147844

Adjacent sequences:  A191405 A191406 A191407 * A191409 A191410 A191411

KEYWORD

dead

AUTHOR

Robert G. Wilson v, Jun 01 2011

EXTENSIONS

Terms corrected by Andrew Howroyd and Robert G. Wilson v, Jul 24 2018

STATUS

approved

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Last modified January 20 14:02 EST 2020. Contains 331094 sequences. (Running on oeis4.)