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Sum of the integer part of 5th roots of positive integers less than or equal to n.
6

%I #23 Sep 28 2024 16:05:07

%S 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,

%T 26,27,28,29,30,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59,61,63,65,

%U 67,69,71,73,75,77,79,81,83,85,87,89,91,93,95,97,99,101,103,105,107

%N Sum of the integer part of 5th roots of positive integers less than or equal to n.

%F G.f.: Sum_{k>=1} x^(k^5)/(1 - x)^2. - _Ilya Gutkovskiy_, Dec 22 2016

%F a(n) = -(1/12) * floor(n^(1/5)) * (-12 - 12*n - floor(n^(1/5)) + 5*floor(n^(1/5))^3 + 6*floor(n^(1/5))^4 + 2*floor(n^(1/5))^5). - _Pooya Farshim_, Sep 28 2024

%t Accumulate[Floor[Surd[Range[0,70],5]]] (* _Harvey P. Dale_, Jan 21 2019 *)

%o (PARI) a(n) = sum(k=1, n, sqrtnint(k, 5)); \\ _Michel Marcus_, Mar 12 2016

%Y Cf. A022554, A031876, A032512.

%Y Partial sums of A178487.

%K nonn

%O 0,3

%A Michel Tixier (tixier(AT)dyadel.net)