A079852 a(1) = 1, a(2) = 2, a(3) = 3 and a(n) is the smallest number such that all a(i)*a(j)*a(k) are different.

1, 2, 3, 4, 5, 7, 9, 11, 13, 16, 17, 19, 23, 25, 29, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 121, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 210, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 289, 293, 307, 311, 313, 317, 331

Offset

1,2

Comments

Note that a(57) = 210 = 2*3*5*7, while 330 = 2*3*5*11 is not in the sequence. This demonstrates that this sequence is not determined by prime signature alone. - Charles R Greathouse IV, Oct 17 2015

Links

Zak Seidov, Table of n, a(n) for n = 1..200

Mathematica

f[l_List] := Block[{k = 1, p2 = Times @@@ Subsets[l, {2}], p3 = Times @@@ Subsets[l, {3}]}, While[Intersection[p3, p2*k] != {}, k++ ]; Append[l, k]]; Nest[f, {1, 2, 3}, 62] (* Ray Chandler, Feb 12 2007 *)

Crossrefs

Cf. A000045, A079850, A066720, A026477.

Sequence in context: A352870 A009087 A026477 * A084400 A050376 A280257

Adjacent sequences: A079849 A079850 A079851 * A079853 A079854 A079855

Keyword

nonn

Author

Amarnath Murthy, Feb 19 2003

Extensions

Extended by Ray Chandler, Feb 12 2007

Typo in name fixed by Zak Seidov, Jul 06 2013

Status

approved