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%I #19 Jun 17 2017 04:00:47
%S 1,4,7,13,19,28,37,49,61,76,91,109,127,148,169,193,217,244,271,301,
%T 331,364,397,433,469,508,547,589,631,676,721,769,817,868,919,973,1027,
%U 1084,1141,1201,1261,1324,1387,1453,1519,1588,1657,1729,1801
%N a(n) = 1 + floor((3/4)*n^2).
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1).
%F a(n) = 1 + floor((3/4)*n^2).
%F G.f.: x*(1+2*x-x^2+x^3) / ( (1+x)*(1-x)^3 ). - _R. J. Mathar_, Aug 25 2011
%F a(n) = 1 + 3*A002620(n). - _R. J. Mathar_, Aug 25 2011
%t c[k_]:=1+Floor[(3/4)k^2];
%t Table[c[k],{k,1,90}]
%o (PARI) a(n)=3*n^2\4+1 \\ _Charles R Greathouse IV_, Oct 16 2015
%Y Cf. A194074 (natural fractal sequence of A194073),
%Y A194075 (natural interspersion of A194074).
%K nonn,easy
%O 1,2
%A _Clark Kimberling_, Aug 14 2011
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