A209492 - cp's OEIS frontend

A209492 a(0)=1; for n >= 1, let k = floor((1 + sqrt(8*n-7))/2), m = n - (k^2 - k+2)/2. Then a(n) = 2^k + 2^(m+1) - 1.

n	a(n)
0	1
1	3
2	5
3	7
4	9
5	11
6	15
7	17
8	19
9	23
10	31
11	33
12	35
13	39
14	47
15	63
16	65
17	67
18	71
19	79
20	95
21	127
22	129
23	131
24	135
25	143
26	159
27	191
28	255
29	257
30	259
31	263
32	271
33	287
34	319
35	383
36	511
37	513
38	515
39	519
40	527
41	543
42	575
43	639
44	767
45	1023
46	1025
47	1027
48	1031
49	1039
50	1055
51	1087
52	1151
53	1279
54	1535
55	2047
56	2049
57	2051
58	2055
59	2063
60	2079
61	2111
62	2175
63	2303
64	2559
65	3071

[1, 3, 5, 7, 9, 11, 15, 17, 19, 23, 31, 33, 35, 39, 47, 63, 65, 67, 71, 79, 95, 127, 129, 131, 135, 143, 159, 191, 255, 257, 259, 263, 271, 287, 319, 383, 511, 513, 515, 519, 527, 543, 575, 639, 767, 1023, 1025, 1027, 1031, 1039, 1055, 1087, 1151, 1279, 1535, 2047, 2049, 2051, 2055, 2063, 2079, 2111, 2175, 2303, 2559, 3071]

cp's OEIS Frontend

A209492 a(0)=1; for n >= 1, let k = floor((1 + sqrt(8*n-7))/2), m = n - (k^2 - k+2)/2. Then a(n) = 2^k + 2^(m+1) - 1.

Table of values

List of values