OFFSET
1,1
COMMENTS
The n-th Moebius polynomial M(n,x) satisfies M(n,-1)=mu(n), the Moebius function of n; thus -1 is a simple root of M(n,x) if n is not squarefree. Hence these values could be called "double nonsquarefree numbers".
The n-th polynomial is divisible by (x+1)^3 for n=175, 343, 513, 800, 875. - T. D. Noe, Jan 09 2008
MATHEMATICA
a[n_, 1]=1; a[n_, k_]:=a[n, k]=Sum[Floor[n/m] a[m, k-1], {m, n-1}]; t={}; Do[p=Table[a[n, k], {k, n}].(x^Range[0, n-1]); If[PolynomialMod[p, (x+1)^2]==0, AppendTo[t, n]], {n, 100}]; t (* T. D. Noe, Jan 09 2008 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre and Paul D. Hanna, Nov 10 2002
EXTENSIONS
More terms from T. D. Noe, Jan 09 2008
STATUS
approved