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

Offset: 1

Author

N. J. A. Sloane, Sep 25 2001

Keywords

• nonn
• nice
• easy

Examples

			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.
		

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

Crossrefs

Cf. A006694, A064287.

Formula

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

Extensions

Extended by Ray Chandler, Apr 25 2008