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 A212179 Number of distinct prime factors of A181800(n) (n-th powerful number that is the first integer of its prime signature). 4
 0, 1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 2, 3, 1, 2, 2, 2, 3, 1, 2, 2, 2, 3, 1, 2, 2, 3, 2, 3, 2, 1, 2, 2, 3, 2, 3, 2, 1, 2, 2, 3, 3, 2, 3, 2, 3, 1, 2, 2, 3, 4, 2, 3, 2, 3, 2, 3, 1, 2, 2, 3, 4, 2, 3, 2, 3, 2, 3, 1, 2, 3, 2, 3, 4, 2, 3, 3, 2, 3, 2, 3, 1, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS Since each prime factor of A181800(n) divides A181800(n) at least twice, this is also the number of exponents > 2 in prime factorization of A181800(n). Length of row A181800(n) of table A212171 equals a(n) for n > 1. Row A181800(n) of table A212172 has the same length when n > 1 (length = 1 if n = 1). LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 Will Nicholes, Prime Signatures FORMULA a(n) = A001221(A181800(n)) = A056170(A181800(n)). EXAMPLE 72 (2^3*3^2) has 2 distinct prime factors. Since 72 = A181800(8), a(8) = 2. CROSSREFS Cf. A181800, A001694, A025487, A212171, A212172, A212176. Sequence in context: A175044 A106149 A253607 * A257023 A238894 A054740 Adjacent sequences:  A212176 A212177 A212178 * A212180 A212181 A212182 KEYWORD nonn AUTHOR Matthew Vandermast, Jun 04 2012 STATUS approved

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Last modified May 15 01:50 EDT 2021. Contains 343909 sequences. (Running on oeis4.)