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A026058 a(n) = (d(n)-r(n))/2, where d = A026057 and r is the periodic sequence with fundamental period (0,0,1,0).

%I A026058 #14 Mar 17 2021 08:54:41
%S A026058 13,25,41,63,90,123,162,209,263,325,395,475,564,663,772,893,1025,1169,
%T A026058 1325,1495,1678,1875,2086,2313,2555,2813,3087,3379,3688,4015,4360,
%U A026058 4725,5109,5513,5937,6383,6850,7339,7850,8385,8943,9525,10131,10763,11420,12103,12812,13549,14313,15105,15925
%N A026058 a(n) = (d(n)-r(n))/2, where d = A026057 and r is the periodic sequence with fundamental period (0,0,1,0).
%H A026058 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,1,-3,3,-1).
%F A026058 a(n) = - 0.125 - 0.125*( - 1)^n + 0.25*cos(n*Pi/2) + (n + 4)*(n^2 + 20*n + 39)/12. [_Richard Choulet_, Dec 13 2008]
%F A026058 G.f.: x^4*( 13-14*x+5*x^2+2*x^3-14*x^4+15*x^5-5*x^6 ) / ( (1+x)*(x^2+1)*(x-1)^4 ). - _R. J. Mathar_, Jun 22 2013
%Y A026058 Cf. A026057.
%K A026058 nonn,easy
%O A026058 4,1
%A A026058 _Clark Kimberling_