A076899 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 denominator of u(n).

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

Offset

1,5

Links

Table of n, a(n) for n=1..80.

Formula

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

Empirical g.f.: -x*(x^14+x^13+x^12-x^11-x^10+2*x^8+2*x^7+x^6-x^5-x^4-x^2-x-1) / ((x-1)*(x^2+x+1)*(x^12+x^6-1)). - Colin Barker, Oct 14 2014

Crossrefs

Cf. A076898 (numerators).

Sequence in context: A206474 A211999 A175025 * A152905 A096601 A078077

Adjacent sequences: A076896 A076897 A076898 * A076900 A076901 A076902

Keyword

frac,nonn

Author

Benoit Cloitre, Nov 26 2002

Status

approved