A064286 - OEIS

A064286

Number of cyclotomic cosets C of 2 mod 2n+1 such that -C = C.

1, 1, 0, 2, 1, 1, 2, 2, 1, 1, 0, 2, 3, 1, 0, 4, 1, 1, 2, 2, 3, 3, 0, 0, 3, 1, 2, 4, 1, 1, 2, 6, 1, 1, 0, 0, 3, 1, 0, 4, 1, 3, 2, 0, 1, 1, 2, 2, 7, 1, 0, 2, 1, 3, 2, 4, 1, 3, 2, 2, 3, 3, 0, 10, 1, 1, 4, 2, 1, 1, 2, 6, 1, 1, 0, 4, 1, 3, 2, 0, 1, 5, 0, 2, 11, 1, 2, 4, 1, 1, 2, 6, 3, 3, 0, 2, 7, 1, 0, 4, 1, 11, 2, 4

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OFFSET

1,4

REFERENCES

F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier/North Holland, 1977, pp. 104-105.

LINKS

Ray Chandler, Table of n, a(n) for n = 1..10000

FORMULA

A006694(n) = a(n) + 2*A064287(n).

EXAMPLE

Mod 15 there are 4 cosets: {1, 2, 4, 8}, {3, 6, 12, 9}, {5, 10}, {7, 14, 13, 11}. Only the cosets {3, 6, 12, 9} and {5, 10} have the desired property. So a(7) = 2.

CROSSREFS

Cf. A006694, A064287.

Sequence in context: A327910 A242998 A140885 * A002471 A218622 A337621

Adjacent sequences: A064283 A064284 A064285 * A064287 A064288 A064289

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane, Sep 25 2001

EXTENSIONS

Extended by Ray Chandler, Apr 25 2008

STATUS

approved