OFFSET
1,12
REFERENCES
B. Cloitre, On strange predictible recursions, preprint 2006
FORMULA
for n>=1 : a(6*n)=4*n-4-(-1)^n, a(6n+1)=0, a(6*n+2)=4*n-3+(-1)^n, a(6*n+3)=4*n-2+2*(-1)^n, a(6*n+4)=(-1)^n, a(6*n+5)=4*n-1+2*(-1)^n.
Empirical g.f.: x^4*(2*x^10+5*x^8+3*x^7+x^6-2*x^5-2*x^4-2*x^3+x^2+x+1) / (x^12-2*x^9+2*x^6-2*x^3+1). - Colin Barker, Jun 28 2013
MATHEMATICA
RecurrenceTable[{a[1]==a[2]==a[3]==0, a[4]==1, a[n]==Abs[a[n-1]-2a[n-2]+ a[n-3]]- a[n-4]}, a, {n, 100}] (* Harvey P. Dale, Mar 13 2014 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Benoit Cloitre, May 31 2006
STATUS
approved