OFFSET

1,10

REFERENCES

See A051664

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = 0 iff n is a prime power. - T. D. Noe, Aug 08 2003

a(n) = (A051664(n)-1)/2 if n is not a prime power and has at most two distinct odd prime divisors. So 105 is the smallest n>1 where neither formula applies. - Aaron Meyerowitz, Apr 18 2018

MATHEMATICA

Table[Count[CoefficientList[Cyclotomic[n, x], x], _?(#<0&)], {n, 0, 100}]

PROG

(PARI) a(n) = #select(x->(x<0), Vec(polcyclo(n))); \\ Michel Marcus, Apr 18 2018

CROSSREFS

KEYWORD

nonn

AUTHOR

Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 03 2003

EXTENSIONS

More terms from T. D. Noe, Aug 08 2003

STATUS

approved