A023618 - OEIS

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A023618 as a simple table

n	a(n)
1	4
2	18
3	42
4	85
5	155
6	272
7	465
8	780
9	1291
10	2121
11	3468
12	5650
13	9182
14	14900
15	24155
16	39131
17	63365
18	102578
19	166029
20	268699
21	434825
22	703624
23	1138552
24	1842282
25	2980944
26	4823341
27	7804403

[4,18,42,85,155,272,465,780,1291,2121,3468,5650, 9182,14900,24155,39131,63365,102578,166029,268699, 434825,703624,1138552,1842282,2980944,4823341, 7804403]