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A043328 a(0)=1; a(1)=1; a(n)= a(n-1) + floor(sqrt(a(n-1)*a(n-2))) + floor(sqrt(a(n-3)*a(n-4))) + .... 1

%I

%S 1,1,2,3,6,11,22,42,83,162,318,623,1224,2402,4717,9261,18185,35706,

%T 70111,137665,270313,530772,1042200,2046413,4018242,7890029,15492492,

%U 30420327,59731927,117286804,230298862,452204027,887926594,1743490958

%N a(0)=1; a(1)=1; a(n)= a(n-1) + floor(sqrt(a(n-1)*a(n-2))) + floor(sqrt(a(n-3)*a(n-4))) + ....

%C Nonlinear recurrence similar to that for Narayana numbers.

%t a[ 0 ]=0; a[ 1 ]=1; a[ 2 ]=1; a[ n_Integer ] := a[ n ]=a[ n-1 ]+ Plus@@Map[ Floor[ Sqrt[ Times@@# ] ]&, Partition[ Reverse[ Array[ a, n, 0 ] ], 2 ] ]

%Y Cf. A002083, A043327.

%K nonn,easy

%O 0,3

%A _Olivier GĂ©rard_, Jul 18 2001.

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Last modified August 19 20:38 EDT 2022. Contains 356231 sequences. (Running on oeis4.)