A128462 Nontrivial products of two lucky numbers.

9, 21, 27, 39, 45, 49, 63, 75, 81, 91, 93, 99, 105, 111, 117, 129, 135, 147, 153, 169, 175, 189, 195, 201, 207, 217, 219, 225, 231, 237, 259, 261, 273, 279, 297, 301, 315, 325, 333, 343, 345, 357, 375, 381, 387, 399, 403, 405, 423, 429, 441, 453, 459, 465, 469

Offset

1,1

Comments

This is to Lucky numbers (A000959) greater than 1, as semiprimes (A001358) are to primes (A000040). Since A000959(1) = 1, dropping the word "nontrivial" gives "product of two lucky numbers" = {a(i)} UNION A000959 = {1, 3, 7, 9, 13, 15, 21, 25, 27, 31, 33, 37, 39, 43, 45, 49, 51, 63, 67, 69, 73, 75, 79, 81, 87, 91, 93, 99, ...}.

Links

Table of n, a(n) for n=1..55.

Formula

Product set of {A000959(n) for n>1} = {A000959(i)*A000959(j) for i, j > 1}.

Crossrefs

Cf. A000959, A001358.

Sequence in context: A053795 A100490 A173250 * A186815 A106214 A348839

Adjacent sequences: A128459 A128460 A128461 * A128463 A128464 A128465

Keyword

easy,nonn

Author

Jonathan Vos Post, May 05 2007

Extensions

99 =3*33 and 175 inserted, sequence extended - R. J. Mathar, Oct 22 2010

Status

approved