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A046756 Number k such that d(k)^4 divides k. 4

%I

%S 1,625,6561,117649,4100625,31250000,37515625,73530625,771895089,

%T 1000000000,2147483648,6442450944,10737418240,15032385536,23622320128,

%U 25937424601,27917287424,32212254720,33059881728,36507222016,40802189312,45097156608,49392123904

%N Number k such that d(k)^4 divides k.

%C Proper subset of A033950, A046754 and A046755. Relatively prime terms are in the sequence together with their products like 73530625 or 771895089000000000.

%e If k=625, d(k) = sigma(0,k) = 5. Its 4th power is 625, which divides k.

%t Select[ Range[ 1, 14500000 ], IntegerQ[ #/(DivisorSigma[ 0, # ])^2 ]& ]

%Y Cf. A033950, A046754, A046755.

%K nonn

%O 1,2

%A _Labos Elemer_

%E a(6)-a(20) from _Donovan Johnson_, Nov 30 2008

%E a(21)-a(23) from _Donovan Johnson_, Jun 08 2011

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Last modified September 25 11:55 EDT 2020. Contains 337342 sequences. (Running on oeis4.)