A184985 - OEIS

%I #48 Jun 19 2019 05:16:48

%S 0,1,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,

%T 27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,

%U 50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70

%N Nonnegative integers excluding 2.

%C Number of adjacent pairs of sectors in a circle with n equal sections.

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).

%F G.f.: (1+x-x^2)*x^2/(1-x)^2. - _Philippe Deléham_, Dec 23 2011

%F a(1) = 0, a(2) = 1, a(n) = n for n > 2. - _Wesley Ivan Hurt_, Jun 17 2019

%p A184985:=n->piecewise(n<3,n-1,n); seq(A184985(n), n=1..100);

%t CoefficientList[Series[(1+x-x^2)*x^2/(1-x)^2, {x,0,50}], x] (* _G. C. Greubel_, Jun 03 2017 *)

%o (PARI) a(n)=n-(n<3) \\ _Charles R Greathouse IV_, Dec 22 2011

%Y Cf. A000027.

%K nonn,easy

%O 1,3

%A _Wesley Ivan Hurt_, Dec 22 2011