login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 13 07:13 EST 2019. Contains 329085 sequences. (Running on oeis4.)