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a(n) = Sum_{j=1..n} floor(j*(1+sqrt(3))); n-th partial sum of Beatty sequence for 1+sqrt(3).
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%I #13 Mar 17 2021 23:43:35

%S 2,7,15,25,38,54,73,94,118,145,175,207,242,280,320,363,409,458,509,

%T 563,620,680,742,807,875,946,1019,1095,1174,1255,1339,1426,1516,1608,

%U 1703,1801,1902,2005,2111,2220,2332,2446,2563,2683,2805,2930,3058

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

%t c[n_] := Sum[Floor[j*(1+Sqrt[3])], {j, 1, n}];

%t c = Table[c[n], {n, 1, 90}]

%o (Python)

%o from sympy import integer_nthroot

%o def A194140(n): return n*(n+1)//2+sum(integer_nthroot(3*j**2,2)[0] for j in range(1,n+1)) # _Chai Wah Wu_, Mar 17 2021

%Y Cf. A054088 (Beatty sequence for 1+sqrt(3)).

%K nonn

%O 1,1

%A _Clark Kimberling_, Aug 17 2011

%E Offset corrected by _Alois P. Heinz_, Mar 17 2021