A081841 - OEIS

%I #7 Aug 20 2013 14:23:52

%S 0,2,4,7,9,11,14,16,19,21,24,26,28,31,33,36,38,40,43,45,48,50,52,55,

%T 57,60,62,65,67,69,72,74,77,79,81,84,86,89,91,94,96,98,101,103,106,

%U 108,110,113,115,118,120,123,125,127,130,132,135,137,139,142,144,147,149,151

%N a(1)=0, a(n)=a(n-1)+3 if n is already in the sequence, a(n)=a(n-1)+2 otherwise.

%F a(1)=0; for n>=1 a(n)=floor(r*n-(4*r-1)/(r+1)) where r=1+sqrt(2)

%K nonn

%O 1,2

%A _Benoit Cloitre_, Apr 11 2003