A043328 - OEIS

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, 1, 2, 3, 6, 11, 22, 42, 83, 162, 318, 623, 1224, 2402, 4717, 9261, 18185, 35706, 70111, 137665, 270313, 530772, 1042200, 2046413, 4018242, 7890029, 15492492, 30420327, 59731927, 117286804, 230298862, 452204027, 887926594, 1743490958

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OFFSET

0,3

COMMENTS

Nonlinear recurrence similar to that for Narayana numbers.

LINKS

Table of n, a(n) for n=0..33.

MATHEMATICA

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 ] ]

CROSSREFS

Cf. A002083, A043327.

Sequence in context: A123341 A372989 A238351 * A141072 A002083 A124973

Adjacent sequences: A043325 A043326 A043327 * A043329 A043330 A043331

KEYWORD

nonn,easy

AUTHOR

Olivier Gérard, Jul 18 2001.

STATUS

approved