|
|
A174239
|
|
a(n) = (3*n + 1 + (-1)^n*(n+3))/4.
|
|
4
|
|
|
1, 0, 3, 1, 5, 2, 7, 3, 9, 4, 11, 5, 13, 6, 15, 7, 17, 8, 19, 9, 21, 10, 23, 11, 25, 12, 27, 13, 29, 14, 31, 15, 33, 16, 35, 17, 37, 18, 39, 19, 41, 20, 43, 21, 45, 22, 47, 23, 49, 24, 51, 25, 53, 26, 55, 27, 57, 28, 59, 29, 61, 30, 63, 31, 65, 32, 67, 33, 69, 34, 71, 35, 73, 36, 75, 37, 77, 38, 79, 39, 81
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
COMMENTS
|
Obtained from A026741 by swapping pairs of consecutive entries.
The main diagonal of an array with this sequence in the top row and further rows defined by the first differences of their previous row is essentially 1 followed by 3*A045623(.):
1, 0, 3, 1, 5, 2, 7, 3, 9, 4, 11, 5, 13, 6, 15, 7, 17, 8, ...
-1, 3, -2, 4, -3, 5, -4, 6, -5, 7, -6, 8, -7, 9, -8, 10, -9, ...
4, -5, 6, -7, 8, -9, 10, -11, 12, -13, 14, -15, 16, -17, ...
-9, 11, -13, 15, -17, 19, -21, 23, -25, 27, -29, 31, ...
20, -24, 28, -32, 36, -40, 44, -48, 52, -56, 60, -64, ...
-44, 52, -60, 68, -76, 84, -92, 100, -108, 116, -124, 132, ...
96, -112, 128, -144, 160, -176, 192, -208, 224, -240, ...
|
|
LINKS
|
|
|
FORMULA
|
a(2n) = 2n+1; a(2n+1) = n.
a(n) = 2*a(n-2) - a(n-4).
a(2n+2) - 2*a(2n+1) = 3.
G.f.: ( 1+x^2+x^3 ) / ( (x-1)^2*(1+x)^2 ). - R. J. Mathar, Feb 07 2011
|
|
MAPLE
|
|
|
MATHEMATICA
|
Table[(3 n + 1 + (-1)^n*(n + 3))/4, {n, 0, 100}] (* Wesley Ivan Hurt, Mar 21 2015 *)
LinearRecurrence[{0, 2, 0, -1}, {1, 0, 3, 1}, 90] (* Harvey P. Dale, Jul 16 2018 *)
|
|
PROG
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|