|
|
A055040
|
|
Numbers of the form 3^(2i+1)*(3*j+2).
|
|
7
|
|
|
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;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Numbers not of the form x^2+y^2+3z^2.
Numbers whose squarefree part is congruent to 6 modulo 9. - Peter Munn, May 17 2020
The asymptotic density of this sequence is 1/8. - Amiram Eldar, Mar 08 2021
|
|
LINKS
|
|
|
FORMULA
|
G.f.: [x(x+2)(x^2+x+1)(x^7+x^3+1)]/(x^11-x^10-x+1) (conjectured).
|
|
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 &] (* Jean-François Alcover, Oct 13 2011 *)
|
|
PROG
|
(Haskell)
a055040 n = a055040_list !! (n-1)
a055040_list = map (* 3) a055048_list
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,nice
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|