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 A323025 Numbers with exactly four distinct exponents in their prime factorization, or four distinct parts in their prime signature. 8
 75600, 105840, 113400, 118800, 126000, 140400, 151200, 158760, 178200, 183600, 198000, 205200, 210600, 211680, 232848, 234000, 237600, 246960, 248400, 252000, 261360, 275184, 275400, 280800, 283500, 294000, 302400, 306000, 307800, 313200, 315000, 334800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Positions of 4's in A071625. Numbers k such that A001221(A181819(k)) = 4. Is a(n) ~ c * n for some c? - David A. Corneth, Jan 09 2019 The asymptotic density of this sequence is (6/Pi^2) * Sum_{n>=2, n squarefree} r(n)/((n-1)*psi(n)) = 0.00035750... (corresponding to c = 2797.1... in the question above, whose answer is affirmative), where psi is the Dedekind psi function (A001615), and r(n) = Sum_{d_1|n, 1

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Last modified July 7 12:08 EDT 2022. Contains 355148 sequences. (Running on oeis4.)