A101561 - cp's OEIS frontend

A101561 a(n) = (-1)^n * [x^n] Sum_{k>=1} x^(k-1)/(1+3*x^k).

n	a(n)
0	1
1	2
2	10
3	29
4	82
5	236
6	730
7	2216
8	6571
9	19604
10	59050
11	177410
12	531442
13	1593596
14	4783060
15	14351123
16	43046722
17	129133838
18	387420490
19	1162281098
20	3486785140
21	10460294156
22	31381059610
23	94143358424
24	282429536563
25	847288078004
26	2541865834900
27	7625599078610

[1, 2, 10, 29, 82, 236, 730, 2216, 6571, 19604, 59050, 177410, 531442, 1593596, 4783060, 14351123, 43046722, 129133838, 387420490, 1162281098, 3486785140, 10460294156, 31381059610, 94143358424, 282429536563, 847288078004, 2541865834900, 7625599078610]

cp's OEIS Frontend

A101561 a(n) = (-1)^n * [x^n] Sum_{k>=1} x^(k-1)/(1+3*x^k).

Table of values

List of values