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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)
OFFSET
1,2
COMMENTS
Next term has 122 digits.
A166469(a(n))=(n+1)! Cf. A000142.
LINKS
EXAMPLE
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.
CROSSREFS
Cf. A000290.
Subsequence of A025487. Also see A002110, A006939, A066120, A166475, A167448.
Sequence in context: A203305 A191954 A344665 * A057527 A166475 A152688
KEYWORD
nonn
AUTHOR
Matthew Vandermast, May 24 2012
STATUS
approved

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Last modified June 17 15:57 EDT 2024. Contains 373463 sequences. (Running on oeis4.)