A228515 Nonlinear recursion: a(n) = a(n-1) + Product_{i=1..(n-1)/2} a(n-2i+1)-a(n-2i).

1, 2, 4, 6, 8, 12, 20, 52, 308, 8500, 2105652, 17181974836, 36028814200938804, 618970019678718951650500916, 22300745198530623760505737951367313156481332

Offset

1,2

Comments

Initial conditions: a(1)=1; a(2)=1; a(3)=4;

With a(3)=3, the recursion gives the positive integers.

Links

Table of n, a(n) for n=1..15.

Mathematica

a[1]:= 1; a[2]:= 2; a[3]:= 4;
a[n_Integer]:=a[n]=a[n-1]+ Times@@Table[(a[n-2i+1]-a[n-2i]), {i, 1, (n-1)/2}];
Table[a[n], {n, 1, 15}]

Crossrefs

Sequence in context: A323114 A362231 A118563 * A363145 A164145 A354530

Adjacent sequences: A228512 A228513 A228514 * A228516 A228517 A228518

Keyword

nonn,easy

Author

Olivier Gérard, Aug 24 2013

Status

approved