A160973 a(n) is the number of positive integers of the form (n-3k)/(2k+1), 1 <= k <= (n-1)/5.
0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 2, 0, 1, 0, 0, 3, 0, 1, 1, 0, 2, 1, 0, 0, 3, 2, 0, 1, 0, 0, 3, 2, 0, 2, 0, 2, 1, 0, 2, 1, 2, 0, 3, 0, 0, 5, 0, 0, 1, 0, 2, 3, 2, 1, 1, 2, 0, 1, 0, 2, 5, 0, 0, 1, 2, 2, 3, 0, 0, 3, 2, 0, 1, 2, 0, 5, 0, 1, 3, 0, 4, 1, 0, 0, 1
Offset: 0
Keywords
Programs
-
Mathematica
a[n_] := Length[Select[Range[Floor[(n-1)/5]], IntegerQ[(n-3#)/(2#+1)] &]]; Array[a, 100, 0] (* Amiram Eldar, Dec 15 2018 *)
-
PARI
a(n) = sum(k=1, (n-1)/5, frac((n-3*k)/(2*k+1)) == 0); \\ Michel Marcus, Dec 15 2018
Extensions
Edited by N. J. A. Sloane, Jun 07 2009
a(44) corrected and more terms from Michel Marcus, Dec 15 2018
Comments