This site is supported by donations to The OEIS Foundation.



Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A212170 a(n) = first counting number with n distinct positive square exponents in its prime factorization. 3
1, 2, 48, 207360, 5643509760000, 74508333765820416000000000, 68238227014337640914957453230080000000000000000, 958098594568198616022876832154309463351366075411333120000000000000000000000000 (list; graph; refs; listen; history; text; internal format)



Next term has 122 digits.

A166469(a(n))=(n+1)! Cf. A000142.


Table of n, a(n) for n=1..8.

D. Alpern, Factorization using the Elliptic Curve Method


a(2) = 48 = 2^4*3^1 has 2 distinct positive square exponents in its prime factorization (4 and 1 are both perfect squares).  48 is the smallest number with this property.

Also, 48 has 3! = 6 divisors that are not divisible by any pair of consecutive primes: 1, 2, 3, 4, 8 and 16. Cf. A166469.


Cf. A000290.

Subsequence of A025487.  Also see A002110, A006939, A066120, A166475, A167448.

Sequence in context: A203778 A203305 A191954 * A057527 A166475 A152688

Adjacent sequences:  A212167 A212168 A212169 * A212171 A212172 A212173




Matthew Vandermast, May 24 2012



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 December 8 18:37 EST 2019. Contains 329865 sequences. (Running on oeis4.)