OFFSET
1,1
COMMENTS
A flat polynomial is defined to be a polynomial whose coefficients are -1, 0, or 1. Sequence A046388 gives the product pq. As proved by Kaplan, given odd primes p < q, it is always possible to find a prime r > q such that Phi(pqr,x) is flat.
LINKS
Nathan Kaplan, Flat cyclotomic polynomials of order three, J. Number Theory 127 (2007), 118-126.
EXAMPLE
a(1)=29 because 15*29 is the least multiple of 15 that produces a flat cyclotomic polynomial.
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, May 15 2009
STATUS
approved