A005469 a(n) = 1 + a(floor(n/2))*a(ceiling(n/2)) for n > 1, a(1) = 2. (Formerly M1398)

2, 5, 11, 26, 56, 122, 287, 677, 1457, 3137, 6833, 14885, 35015, 82370, 194300, 458330, 986390, 2122850, 4570610, 9840770, 21435122, 46689890, 101709206, 221563226, 521198276, 1226050226, 2884185551, 6784816901, 16004491001, 37752490001, 89053519001

Offset

1,1

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..31.

Maple

a:= proc(n) option remember; `if`(n=1, 2,
      1+(t->a(t)*a(n-t))(iquo(n, 2)))
    end:
seq(a(n), n=1..35);  # Alois P. Heinz, Jul 04 2019

Mathematica

a[n_] := a[n] = If[n==1, 2, 1 + a[Floor[n/2]] a[Ceiling[n/2]]];
a /@ Range[35] (* Jean-François Alcover, Nov 16 2020 *)

Crossrefs

Cf. A005468.

Sequence in context: A085945 A365322 A371662 * A218575 A159929 A362740

Adjacent sequences: A005466 A005467 A005468 * A005470 A005471 A005472

Keyword

nonn

Author

Colin Mallows

Status

approved