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 A199768 Numbers whose greatest prime factor is less than their number of divisors. 2
 4, 6, 8, 12, 16, 18, 20, 24, 27, 30, 32, 36, 40, 42, 45, 48, 50, 54, 56, 60, 64, 70, 72, 75, 80, 81, 84, 90, 96, 100, 105, 108, 112, 120, 126, 128, 132, 135, 140, 144, 150, 160, 162, 168, 180, 189, 192, 196, 198, 200, 210, 216, 220, 224, 225, 240, 243, 250, 252 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The greatest prime factor equals the number of divisors only for 1 (as defined in A006530) and numbers of the form p^(p-1) for p a prime. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 4 has 2 as its greatest prime factor, and it has 3 factors (1, 2, 4), so it is in the sequence. 10 has 5 as its greatest prime factor, but it has only 4 factors (1, 2, 5, 10), so it is not in the sequence. MATHEMATICA Select[Range[300], FactorInteger[#][[-1, 1]]

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Last modified June 22 07:58 EDT 2024. Contains 373565 sequences. (Running on oeis4.)