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A055040
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Numbers of the form 3^(2i+1)*(3*j+2).
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1
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6, 15, 24, 33, 42, 51, 54, 60, 69, 78, 87, 96, 105, 114, 123, 132, 135, 141, 150, 159, 168, 177, 186, 195, 204, 213, 216, 222, 231, 240, 249, 258, 267, 276, 285, 294, 297, 303, 312, 321, 330, 339, 348, 357, 366, 375, 378, 384, 393, 402, 411
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Numbers not of the form x^2+y^2+3z^2.
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REFERENCES
| L. J. Mordell, A new Waring's problem with squares of linear forms, Quart. J. Math., 1 (1930), 276-288 (see p. 283).
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FORMULA
| G.f.: [x(x+2)(x^2+x+1)(x^7+x^3+1)]/(x^11-x^10-x+1) (conjectured).
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MATHEMATICA
| max = 500; Select[ Union[ Flatten[ Table[3^(2*i + 1)*(3*j + 2), {i, 0, Ceiling[ Log[max/6]/Log[9]]}, {j, 0, Ceiling[(max/9^i - 6)/9]}]]], # <= max &] (* From Jean-François Alcover, Oct 13 2011 *)
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CROSSREFS
| Equals 3*A055048(n).
Sequence in context: A187918 A190747 A043477 * A017233 A122709 A052220
Adjacent sequences: A055037 A055038 A055039 * A055041 A055042 A055043
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 01 2000
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