Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #21 Jun 05 2015 03:51:50
%S 0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,
%T 0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,
%U 0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0
%N Eventual fixed point of map x -> floor(tan(x)) when starting the iteration with the initial value x = n.
%C Note that this sequence lists the terminating values only for the nonnegative starting points of the iteration map, although the function is defined in all Z and the intermediate steps in iteration may visit also negative numbers.
%C Pohjola conjectures that no other numbers than 0 and 1 will ever occur in this sequence.
%C In any case, any strictly positive term present in this sequence must be one of the terms of A249836.
%H Antti Karttunen, <a href="/A258021/b258021.txt">Table of n, a(n) for n = 0..10000</a>
%F If n is equal to floor(tan(n)), then a(n) = n, and for any other n (positive or negative), a(n) = a(floor(tan(n))). [Recurrence defined in whole Z.]
%o (Scheme) (define (A258021 n) (if (= n (floor->exact (tan n))) n (A258021 (floor->exact (tan n)))))
%Y Cf. A000503, A258020, A258202, A249836.
%Y Cf. also A258022 (positions of terms <= 0), A258024 (positions of terms >= 1), A258201 (the smallest number visited in the iteration).
%K nonn
%O 0
%A _V.J. Pohjola_ & _Antti Karttunen_, May 24 2015