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a(n) = Sum_{j=1..n} floor(j*(1+sqrt(3))/2); n-th partial sum of Beatty sequence A003511.
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%I #21 Jul 31 2023 06:57:14

%S 1,3,7,12,18,26,35,45,57,70,85,101,118,137,157,178,201,225,250,277,

%T 305,335,366,398,432,467,503,541,580,620,662,705,750,796,843,892,942,

%U 993,1046,1100,1156,1213,1271,1331,1392,1454,1518,1583,1649,1717

%N a(n) = Sum_{j=1..n} floor(j*(1+sqrt(3))/2); n-th partial sum of Beatty sequence A003511.

%H G. C. Greubel, <a href="/A194117/b194117.txt">Table of n, a(n) for n = 1..1000</a>

%t a[n_] := Sum[Floor[j*(1+Sqrt[3])/2], {j, 1, n}]; Table[a[n], {n, 1, 90}]

%t With[{c=(1+Sqrt[3])/2},Accumulate[Floor[c*Range[50]]]] (* _Harvey P. Dale_, Aug 02 2012 *)

%Y Cf. A003511 (Beatty sequence for (1+sqrt(3))/2).

%K nonn

%O 1,2

%A _Clark Kimberling_, Aug 16 2011

%E Definition corrected by _Georg Fischer_, Jul 31 2023