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A267807 a(0) = a(1) = 1; for n>1, a(n) = (a(n-1) mod 3) + a(n-2).

%I A267807 #16 Jan 22 2016 11:20:52
%S A267807 1,1,2,3,2,5,4,6,4,7,5,9,5,11,7,12,7,13,8,15,8,17,10,18,10,19,11,21,
%T A267807 11,23,13,24,13,25,14,27,14,29,16,30,16,31,17,33,17,35,19,36,19,37,20,
%U A267807 39,20,41,22,42,22,43,23,45,23,47,25,48,25,49,26,51,26,53,28
%N A267807 a(0) = a(1) = 1; for n>1, a(n) = (a(n-1) mod 3) + a(n-2).
%H A267807 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,0,0,0,0,0,1,0,-1).
%F A267807 G.f.: (1 + x + x^2 + 2*x^3 + 2*x^5 + 2*x^6 + x^7 - x^8)/((1 - x)^2*(1 + x)^2* (1 + x^2)*(1 + x^4)). [_Bruno Berselli_, Jan 21 2016]
%F A267807 a(n) = a(n-2) + a(n-8) - a(n-10) for n>9. [_Bruno Berselli_, Jan 21 2016]
%t A267807 RecurrenceTable[{a[0] == a[1] == 1, a[n] == Mod[a[n - 1], 3] + a[n - 2]}, a, {n, 90}]
%t A267807 LinearRecurrence[{0, 1, 0, 0, 0, 0, 0, 1, 0, -1}, {1, 1, 2, 3, 2, 5, 4, 6, 4, 7}, 90] (* _Bruno Berselli_, Jan 21 2016 *)
%o A267807 (PARI) a=vector(100); for(n=1, #a, if(n<3, a[n]=1, a[n]=a[n-1]%3+a[n-2])); a \\ _Colin Barker_, Jan 22 2016
%Y A267807 Cf. A000045, A267806, A267808, A267809.
%K A267807 nonn,easy
%O A267807 0,3
%A A267807 _José María Grau Ribas_, Jan 20 2016
%E A267807 Edited by _Bruno Berselli_, Jan 21 2016