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A066724 a(1) = 1, a(2) = 2; for n > 1, a(n) is the least integer > a(n-1) such that the products a(i)*a(j) for 1 <= i < j <= n are all distinct. 8
1, 2, 3, 4, 5, 7, 9, 11, 13, 16, 17, 19, 23, 25, 29, 30, 31, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 81, 83, 84, 89, 97, 101, 103, 107, 109, 113, 121, 127, 128, 131, 137, 139, 149, 151, 154, 157, 163, 167, 169, 173, 179, 180, 181, 191, 193, 197, 199, 211 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The first 15 terms are the same as A026477; the first 13 terms are the same as A026416.

Contains all primes. - Ivan Neretin, Mar 02 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..1000

EXAMPLE

a(7) is not 10 because we already have 10 = 2*5. Of course all primes appear. a(14) is not 24 because if it was there would be a repeat among the terms a(i)*a(j) for 1 <= i < j <= 14, namely 3*16 = 2*24.

MATHEMATICA

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

CROSSREFS

Cf. A000028, A026477, A026416, A050376, A084400.

Cf. A080431.

Cf. A079851.

Sequence in context: A000028 A026416 A123193 * A089237 A009087 A026477

Adjacent sequences:  A066721 A066722 A066723 * A066725 A066726 A066727

KEYWORD

easy,nonn

AUTHOR

Robert E. Sawyer (rs.1(AT)mindspring.com), Jan 18 2002

STATUS

approved

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Last modified November 17 08:39 EST 2019. Contains 329217 sequences. (Running on oeis4.)