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%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
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