A076898 Let u(1)=u(2)=u(3)=1, u(n)=sign(u(n-1)-u(n-2))/(u(n-3)+1); then a(n) is the numerator of u(n).

1, 1, 1, 0, -1, -1, 0, 2, 2, 0, -1, -1, 0, 3, 3, 0, -2, -2, 0, 5, 5, 0, -3, -3, 0, 8, 8, 0, -5, -5, 0, 13, 13, 0, -8, -8, 0, 21, 21, 0, -13, -13, 0, 34, 34, 0, -21, -21, 0, 55, 55, 0, -34, -34, 0, 89, 89, 0, -55, -55, 0, 144, 144, 0, -89, -89, 0, 233, 233, 0, -144, -144, 0, 377, 377, 0, -233, -233, 0, 610, 610, 0, -377, -377, 0, 987

Offset

1,8

Links

Table of n, a(n) for n=1..86.

Formula

F(k) denotes the k-th Fibonacci number: a(6k)=-F(k); a(6k+1)=0; a(6k+2)=a(6k+3)=F(k+2); a(6k+4)=0; a(6k+5)=-F(k+1).

Empirical g.f.: x*(x^12-x^8-x^7+x^6+x^5+x^4-x^2-x-1) / (x^12+x^6-1). - Colin Barker, Oct 14 2014

Crossrefs

Cf. A076899 (denominators).

Sequence in context: A287447 A110568 A088689 * A174294 A089385 A124407

Adjacent sequences: A076895 A076896 A076897 * A076899 A076900 A076901

Keyword

frac,sign

Author

Benoit Cloitre, Nov 26 2002

Status

approved