A075022 - cp's OEIS frontend

A075022 a(1) = 1; for n>1, a(n) = the largest prime divisor of the number C(n) formed from the concatenation of 1,2,3,... up to n.

n	a(n)
1	1
2	3
3	41
4	617
5	823
6	643
7	9721
8	14593
9	3803
10	1234567891
11	630803
12	2110805449
13	869211457
14	205761315168520219
15	8230452606740808761
16	1231026625769
17	584538396786764503
18	801309546900123763
19	833929457045867563

[1, 3, 41, 617, 823, 643, 9721, 14593, 3803, 1234567891, 630803, 2110805449, 869211457, 205761315168520219, 8230452606740808761, 1231026625769, 584538396786764503, 801309546900123763, 833929457045867563]

cp's OEIS Frontend

A075022 a(1) = 1; for n>1, a(n) = the largest prime divisor of the number C(n) formed from the concatenation of 1,2,3,... up to n.

Table of values

List of values