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A086849
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Sum of first n nonsquares.
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10
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2, 5, 10, 16, 23, 31, 41, 52, 64, 77, 91, 106, 123, 141, 160, 180, 201, 223, 246, 270, 296, 323, 351, 380, 410, 441, 473, 506, 540, 575, 612, 650, 689, 729, 770, 812, 855, 899, 944, 990, 1037, 1085, 1135, 1186, 1238, 1291, 1345, 1400, 1456, 1513, 1571, 1630
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history;
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = Sum_{i=1..n} (i + floor(1/2 + sqrt(i))).
a(n) = floor(1/2 + (n + sqrt(n))*(n/2 + sqrt(n)/6 + 1/3) - (floor(1/2 + sqrt(n)) - sqrt(n))^2*sqrt(n)). - Graeme McRae, Aug 28 2007
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MATHEMATICA
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PROG
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(Haskell)
a086849 n = a086849_list !! (n-1)
a086849_list = scanl1 (+) a000037_list
(PARI) a(n)=my(k=n+(sqrtint(4*n)+1)\2, s=sqrtint(k)); k*(k+1)/2 - s*(s+1)*(2*s+1)/6 \\ Charles R Greathouse IV, Aug 28 2016
(Python)
from math import isqrt
def A086849(n): return (m:= n + isqrt(n + isqrt(n)))*(m + 1)//2 - (k:=isqrt(m))*(k + 1)*(2*k + 1)//6 # Chai Wah Wu, Mar 31 2022
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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