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%I #35 Dec 27 2023 11:54:15
%S 0,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
%T 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
%U 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
%N a(0) = 0, a(1) = 1, a(n) = a(a(n-1)) + a(a(n-2)) if n > 1.
%C Partial sums are A004275. Binomial transform is A048492, starting with 0. - _Paul Barry_, Feb 28 2003
%D Sequence proposed by Reg Allenby.
%H Ömür Deveci, Zafer Adıgüzel, and Taha Doğan, <a href="https://doi.org/10.7546/nntdm.2020.26.1.179-190">On the Generalized Fibonacci-circulant-Hurwitz numbers</a>, Notes on Number Theory and Discrete Mathematics (2020) Vol. 26, No. 1, 179-190.
%H O. Deveci, Y. Akuzum, E. Karaduman, and O. Erdag, <a href="http://dx.doi.org/10.5539/jmr.v7n2p34">The Cyclic Groups via Bezout Matrices</a>, Journal of Mathematics Research, Vol. 7, No. 2, 2015, pp. 34-41.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Fibonaccin-StepNumber.html">Fibonacci n-Step Number</a>
%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).
%F G.f.: x*(1+x^2)/(1-x). - _Paul Barry_, Feb 28 2003
%t CoefficientList[Series[x (1 + x^2)/(1 - x), {x, 0, 104}], x] (* or *)
%t Nest[Append[#, #[[#[[-1]] + 1]] + #[[#[[-2]] + 1 ]]] &, {0, 1}, 105] (* _Michael De Vlieger_, Jul 31 2020 *)
%o (PARI) a(n)=(n>0)+(n>2)
%Y Cf. A004275, A048492.
%K nonn,easy
%O 0,4
%A _N. J. A. Sloane_, _R. K. Guy_
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