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A160664
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a(n) = a(n-1) + A000203(n), a(0)=1.
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4
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1, 2, 5, 9, 16, 22, 34, 42, 57, 70, 88, 100, 128, 142, 166, 190, 221, 239, 278, 298, 340, 372, 408, 432, 492, 523, 565, 605, 661, 691, 763, 795, 858, 906, 960, 1008, 1099, 1137, 1197, 1253, 1343, 1385, 1481
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graph;
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listen;
history;
text;
internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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MAPLE
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ListTools:-PartialSums(map(numtheory:-sigma, [1, $1..100])); # Robert Israel, Dec 19 2016
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MATHEMATICA
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lst = {1}; a = 1; Do[a = a + DivisorSigma[1, n]; AppendTo[lst, a], {n, 80}]; lst (* Carl Najafi, Aug 21 2011 *)
Transpose[NestList[{First[#]+1, Last[#]+DivisorSigma[1, First[#]+1]}&, {0, 1}, 50]][[2]] (* Harvey P. Dale, May 05 2012 *)
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PROG
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(Python)
from math import isqrt
def A160664(n): return (-(s:=isqrt(n))**2*(s+1) + sum((q:=n//k)*((k<<1)+q+1) for k in range(1, s+1))>>1)+1 # Chai Wah Wu, Oct 22 2023
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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