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%I #22 Nov 21 2022 09:38:35
%S 1,3,4,6,12,8,18,12,14,24,24,18,20,32,36,24,42,30,72,32,48,54,48,38,
%T 60,56,42,96,44,72,48,72,54,72,80,90,60,62,96,84,144,68,96,144,72,74,
%U 114,96,168,80,126,84,108,132,120,90,112,128,144,120,98,102,216,104,192
%N Sum of divisors of the squarefree numbers: sigma(A005117(n)).
%H Harvey P. Dale, <a href="/A062822/b062822.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = Product_{k=1..A001221(n)} (A265668(n,k) + 1). - _Reinhard Zumkeller_, Dec 13 2015
%F From _Amiram Eldar_, Nov 21 2022: (Start)
%F a(n) = A000203(A005117(n)).
%F Sum_{k=1..n} a(k) ~ c * n^2, where c = Pi^4/(72*zeta(3)) = A152649 / A002117 = 1.1254908... . (End)
%t DivisorSigma[1,#]&/@Select[Range[150],SquareFreeQ] (* _Harvey P. Dale_, May 18 2014 *)
%o (PARI) j=[]; for(n=1,200, if(issquarefree(n),j=concat(j, sigma(n)))); j
%o (Haskell)
%o a062822 1 = 1
%o a062822 n = product $ map (+ 1) $ a265668_row n
%o -- _Reinhard Zumkeller_, Dec 13 2015
%Y Cf. A000203, A005117, A002117, A152649, A265668, A001221.
%K nonn
%O 1,2
%A _Jason Earls_, Jul 20 2001
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