%I #11 Jun 19 2012 19:06:42
%S 1,2,5,6,9,10,13,16,17,20,23,24,27,30,33,34,37,40,43,44,47,50,53,56,
%T 57,60,63,66,69,70,73,76,79,82,85,86,89,92,95,98,101,102,105,108,111,
%U 114,117,120,121,124,127,130,133,136,139,140,143,146,149,152,155
%N 3*n - 2*floor(sqrt(4*n+5)) + 5.
%H T. D. Noe, <a href="/A000277/b000277.txt">Table of n, a(n) for n = 0..1000</a>
%t Table[3*n - 2*Floor[Sqrt[4 n + 5]] + 5, {n, 0, 100}] (* _T. D. Noe_, Jun 19 2012 *)
%o (PARI) a(n)=3*n-2*sqrtint(4*n+5)+5
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, based on a message from Michael S. Cann Jr. (mscannjr(AT)gmail.com)