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A026068 (d(n)-r(n))/5, where d = A026066 and r is the periodic sequence with fundamental period (0,3,1,0,1).

%I A026068 #15 Oct 21 2022 21:29:47
%S A026068 21,33,49,68,90,116,145,179,217,259,306,357,414,476,543,616,694,779,
%T A026068 870,967,1071,1181,1299,1424,1556,1696,1843,1999,2163,2335,2516,2705,
%U A026068 2904,3112,3329,3556,3792,4039,4296,4563,4841,5129,5429,5740,6062,6396,6741
%N A026068 (d(n)-r(n))/5, where d = A026066 and r is the periodic sequence with fundamental period (0,3,1,0,1).
%H A026068 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (3, -3, 1, 0, 1, -3, 3, -1).
%F A026068 a(n)=(n + 7)*(n^2 + 35*n + 90)/30 - 1/5*(1 + ( - 1/2 + 3/10*5^(1/2))*cos(2*n*Pi/5) + (1/5*2^(1/2)*(5 + 5^(1/2))^(1/2) + 1/10*2^(1/2)*(5 - 5^(1/2))^(1/2))*sin(2*n*Pi/5) + ( - 1/2 - 3/10*5^(1/2))*cos(4*n*Pi/5) + ( - 1/10*2^(1/2)*(5 + 5^(1/2))^(1/2) + 1/5*2^(1/2)*(5 - 5^(1/2))^(1/2))*sin(4*n*Pi/5)) - _Richard Choulet_, Dec 14 2008
%F A026068 a(n)= 3*a(n-1) -3*a(n-2) +a(n-3) +a(n-5) -3*a(n-6) +3*a(n-7) -a(n-8). G.f.: -x^7*(-21+30*x-13*x^2+x^3+20*x^5-29*x^6+11*x^7)/( (x^4+x^3+x^2+x+1) * (x-1)^4). - _R. J. Mathar_, Oct 05 2009
%t A026068 LinearRecurrence[{3,-3,1,0,1,-3,3,-1},{21,33,49,68,90,116,145,179},60] (* _Harvey P. Dale_, Sep 10 2014 *)
%Y A026068 Cf. A152892.
%K A026068 nonn,easy
%O A026068 7,1
%A A026068 _Clark Kimberling_
%E A026068 Corrected by _T. D. Noe_, Dec 11 2006