OFFSET
1,1
COMMENTS
LINKS
R. Zumkeller, Table of n, a(n) for n = 1..10000
Peter Luschny, Zumkeller Numbers
MATHEMATICA
ZumkellerQ[n_] := Module[{d = Divisors[n], t, ds, x}, ds = Total[d]; If[Mod[ds, 2] > 0, False, t = CoefficientList[Product[1 + x^i, {i, d}], x]; t[[1 + ds/2]] > 0]];
a[n_] := Sum[Boole[ZumkellerQ[k]], {k, n, n + 11}];
Array[a, 105] (* Jean-François Alcover, Apr 30 2017, after T. D. Noe *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 19 2010
STATUS
approved