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A097919 a(1)=1; a(n+1) = Sum_{k=1 to n} a(k) a(ceiling(n/k)). 3
1, 1, 2, 5, 13, 35, 92, 246, 646, 1705, 4475, 11755, 30790, 80738, 211424, 553780, 1449999, 3796903, 9940710, 26027151, 68140743, 178399767, 467059142, 1222789414, 3201309100, 8381170779, 21942203523, 57445520528, 150394362117, 393737778753, 1030818974142 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

MAPLE

f:=proc(n) option remember; local k; if n = 1 then RETURN(1); fi; add( f(k)*f(ceil((n-1)/k)), k=1..n-1 ); end;

MATHEMATICA

a[1] := 1; a[n_] := a[n] = Sum[a[k]*a[Ceiling[(n - 1)/k]], {k, 1, n - 1}]; Table[a[n], {n, 1, 30}] (* G. C. Greubel, Dec 20 2017 *)

CROSSREFS

Cf. A097417.

Sequence in context: A137674 A048781 A291242 * A160438 A240609 A054657

Adjacent sequences:  A097916 A097917 A097918 * A097920 A097921 A097922

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, following a suggestion of Benoit Cloitre, Sep 03 2004

STATUS

approved

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Last modified May 20 03:10 EDT 2019. Contains 323412 sequences. (Running on oeis4.)