| 0, 0, 0, 1, 2, 3, 5, 7, 9, 12, 15, 18, 22, 26, 30, 35, 40, 45, 51, 57, 63, 70, 77, 84, 92, 100, 108, 117, 126, 135, 145, 155, 165, 176, 187, 198, 210, 222, 234, 247, 260, 273, 287, 301, 315, 330, 345, 360, 376, 392, 408, 425, 442, 459, 477, 495, 513, 532, 551, 570
(list; graph; listen)
|
|
|
OFFSET
|
0,5
|
|
|
COMMENT
|
Complementary with A130481 regarding triangular numbers, in that A130481(n)+3*a(n)=n(n+1)/2=A000217(n).
Apart from offset, the same as A062781. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 13 2008
|
|
FORMULA
|
a(n)=1/2*floor(n/3)*(2n-1-3*floor(n/3))))=A002264(n)*(2n-1-3*A002264(n))/2. Also: a(n)=1/2*A002264(n)*(n-1+A010872(n)). G.f.: g(x)=x^3/((1-x^3)(1-x)^2).
|
|
CROSSREFS
|
Cf. A002265, A002266, A004526, A010872, A010873, A010874, A062781, A130482, A130483.
Adjacent sequences: A130515 A130516 A130517 this_sequence A130519 A130520 A130521
Sequence in context: A071423 A062781 A058937 this_sequence A001840 A130206 A022794
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 01 2007
|
|
