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 A046756 Number k such that d(k)^4 divides k. 4
 1, 625, 6561, 117649, 4100625, 31250000, 37515625, 73530625, 771895089, 1000000000, 2147483648, 6442450944, 10737418240, 15032385536, 23622320128, 25937424601, 27917287424, 32212254720, 33059881728, 36507222016, 40802189312, 45097156608, 49392123904 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Proper subset of A033950, A046754 and A046755. Relatively prime terms are in the sequence together with their products like 73530625 or 771895089000000000. LINKS EXAMPLE If k=625, d(k) = sigma(0,k) = 5. Its 4th power is 625, which divides k. MATHEMATICA Select[ Range[ 1, 14500000 ], IntegerQ[ #/(DivisorSigma[ 0, # ])^2 ]& ] CROSSREFS Cf. A033950, A046754, A046755. Sequence in context: A250431 A046755 A016816 * A143026 A238700 A064781 Adjacent sequences:  A046753 A046754 A046755 * A046757 A046758 A046759 KEYWORD nonn AUTHOR EXTENSIONS a(6)-a(20) from Donovan Johnson, Nov 30 2008 a(21)-a(23) from Donovan Johnson, Jun 08 2011 STATUS approved

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Last modified September 26 02:27 EDT 2021. Contains 347664 sequences. (Running on oeis4.)