OFFSET
1,3
COMMENTS
Numbers k such that the sum of first n nonnegative noncomposite numbers is equal to 3k.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
1/3 + 2/3 = 1, 1/3 + 2/3 + 3/3 = 2, 1/3 + 2/3 + 3/3 + 5/3 + 7/3 = 6.
MATHEMATICA
s = 1; t = {0}; Do[s = s + Prime[n]; If[Mod[s, 3] == 0, AppendTo[t, s/3]], {n, 200}]; t (* T. D. Noe, Apr 18 2012 *)
Select[Accumulate[Join[{0, 1/3}, Prime[Range[200]]/3]], IntegerQ] (* Harvey P. Dale, Mar 06 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Gerasimov Sergey, Apr 15 2012
EXTENSIONS
Definition corrected by Harvey P. Dale, Mar 06 2016
STATUS
approved