A109944 - cp's OEIS frontend

A109944 a(1) = 1, a(n) = smallest prime number beginning with n if n is composite or vice versa. If n is prime a(n) = 10n.

n	a(n)
1	1
2	20
3	30
4	41
5	50
6	61
7	70
8	83
9	97
10	101
11	110
12	127
13	130
14	149
15	151
16	163
17	170
18	181
19	190
20	2003
21	211
22	223
23	230
24	241
25	251
26	263
27	271
28	281
29	290
30	307
31	310
32	3203
33	331
34	347
35	353
36	367
37	370
38	383
39	397
40	401
41	410
42	421
43	430
44	443
45	457
46	461
47	470
48	487
49	491
50	503
51	5101
52	521
53	530
54	541

[1, 20, 30, 41, 50, 61, 70, 83, 97, 101, 110, 127, 130, 149, 151, 163, 170, 181, 190, 2003, 211, 223, 230, 241, 251, 263, 271, 281, 290, 307, 310, 3203, 331, 347, 353, 367, 370, 383, 397, 401, 410, 421, 430, 443, 457, 461, 470, 487, 491, 503, 5101, 521, 530, 541]

cp's OEIS Frontend

A109944 a(1) = 1, a(n) = smallest prime number beginning with n if n is composite or vice versa. If n is prime a(n) = 10n.

Table of values

List of values