A330293 - cp's OEIS frontend

A330293 a(1) = 1, a(2) = 2; for n > 2, a(n) = the smallest prime divisor of the number formed by the concatenation of a(1) to a(n-1) that has not previously appeared in the sequence.

n	a(n)
1	1
2	2
3	3
4	41
5	7
6	653
7	331
8	2536483
9	191
10	176081
11	18307
12	2143406938831
13	101
14	73
15	3541
16	439
17	5665417
18	37
19	17302849
20	86113
21	11
22	878390431
23	2969
24	1385625388248048145493629820571541645230648738185397486740279040908468652182116663161996667
25	59
26	30956837
27	181
28	151
29	159833
30	1629097816565791058167
31	293
32	2063
33	3251
34	31219483
35	13

[1, 2, 3, 41, 7, 653, 331, 2536483, 191, 176081, 18307, 2143406938831, 101, 73, 3541, 439, 5665417, 37, 17302849, 86113, 11, 878390431, 2969, 1385625388248048145493629820571541645230648738185397486740279040908468652182116663161996667, 59, 30956837, 181, 151, 159833, 1629097816565791058167, 293, 2063, 3251, 31219483, 13]

cp's OEIS Frontend

A330293 a(1) = 1, a(2) = 2; for n > 2, a(n) = the smallest prime divisor of the number formed by the concatenation of a(1) to a(n-1) that has not previously appeared in the sequence.

Table of values

List of values