OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
Floor(15/6)=2, floor(21/6)=3, floor(45/6)=7,..
MATHEMATICA
f[n_]:=n*(n+1)/2; lst={}; Do[If[PrimeQ[p=Floor[f[n]/6]], AppendTo[lst, p]], {n, 7!}]; lst
Select[Floor[#/6]&/@Accumulate[Range[1000]], PrimeQ] (* Harvey P. Dale, Jul 23 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Dec 12 2009
STATUS
approved