OFFSET
1,2
COMMENTS
Cyclic shifts correspond to multiplication by a root of unity.
a(n)=2 for n prime, corresponding to the empty and the full subset. - Joerg Arndt, Jun 10 2011
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..164
Joerg Arndt, Matters Computational (The Fxtbook), section 18.4 "Sums of roots of unity that are zero", p. 383.
FORMULA
EXAMPLE
a(6) = 5 because these subsets add to zero: (left: as bitstring, right: subset)
...... (empty sum)
..1..1 0 3
.1.1.1 0 2 4
.11.11 0 1 3 4
111111 0 1 2 3 4 5 (all roots of unity)
CROSSREFS
KEYWORD
nonn
AUTHOR
Joerg Arndt, Aug 30 2009
EXTENSIONS
a(32)-a(39) from Joerg Arndt, Jun 10 2011
Terms a(40) onward from Max Alekseyev, Apr 08 2013
STATUS
approved