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A061299
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Least number such that number of divisors is n-th term from the product of 3 distinct primes sequence A007304.
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7
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720, 2880, 46080, 25920, 184320, 2949120, 129600, 414720, 11796480, 1658880, 188743680, 3732480, 2073600, 26542080, 12079595520, 14929920, 48318382080, 106168320, 8294400, 3092376453120, 1698693120, 18662400, 238878720
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n)=A005179[A007304(n)]; Min{x; A000005(x)=pqr} p, q, r are distinct primes. If k=pqr, p>q>r then A005179(k)=2^(p-1)*3^(q-1)*5^(r-1).
A000005(a(n))=A007304(n) and A000005(m)<>A007304(n) for m<a(n); a(n) = A005179(A007304(n)); a(p*m*q) = 2^(q-1) * 3^(m-1) * 5^(p-1) for primes p<m<q; a(A000040(i)*A000040(j)*A000040(k)) = 2^(A084127(k)-1) * 3^(A084127(j)-1) * 5^(A084127(i)-1) for i<j<k. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 15 2004
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EXAMPLE
| n=5, A007304(5)=78=2.3.13, A005179(78)=184320= (2^12)*(3^2)*(5^1)=a(5) All terms are divisible by a(1)=720, the first entry. All terms[=a(j)], not only arguments[=j] have 3 distinct prime factors at exponents determined by the p,q,r factors of their arguments: a(pqr)=RPQ.
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CROSSREFS
| Cf. A000005, A005179, A007304, A061148, A061149.
Cf. A096932, A061234, A061286.
Sequence in context: A052800 A052794 A096933 * A167563 A202095 A187290
Adjacent sequences: A061296 A061297 A061298 * A061300 A061301 A061302
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Jun 05 2001
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Apr 20 2007
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