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a(1)=1, a(n+1) = Sum_{k=1..floor(sqrt(n))} a(floor(k*sqrt(n))).
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%I #8 Sep 16 2015 13:03:03

%S 1,1,1,1,2,2,2,3,3,6,6,6,9,9,9,9,19,19,19,32,32,32,32,32,32,81,81,81,

%T 130,130,130,130,130,140,189,189,378,378,378,567,567,567,567,619,619,

%U 821,821,831,831,1711,1711,1711,2591,2640,2692,2881,2881,2881,3761,3963

%N a(1)=1, a(n+1) = Sum_{k=1..floor(sqrt(n))} a(floor(k*sqrt(n))).

%t a = {1}; Do[AppendTo[a, Sum[a[[Floor[k*Sqrt[n - 1]]]], {k, 1, Floor[Sqrt[n - 1]]}]], {n, 2, 100}]; a (* _Stefan Steinerberger_, Sep 18 2007 *)

%K nonn

%O 1,5

%A _Leroy Quet_, Sep 16 2007

%E More terms from _Stefan Steinerberger_, Sep 18 2007