A043327 a(0)=1; a(1)=1; a(n)= a(n-1) + floor( sqrt(a(n-1)*a(n-2))+ sqrt(a(n-3)*a(n-4))+ ... ).

1, 1, 2, 3, 6, 11, 22, 43, 85, 166, 327, 641, 1259, 2471, 4853, 9528, 18710, 36737, 72137, 141643, 278125, 546112, 1072322, 2105559, 4134379, 8118070, 15940263, 31299549, 61458328, 120676683, 236955071, 465273846, 913589879, 1793882179

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

Crossrefs

Cf. A002083, A043328.

Sequence in context: A124973 A318123 A226594 * A247968 A005578 A058050

Adjacent sequences: A043324 A043325 A043326 * A043328 A043329 A043330

Keyword

nonn,easy

Author

Olivier Gérard, Jul 18 2001.

Status

approved