A288070 - cp's OEIS frontend

A288070 a(n) is the least number that enters a cycle of length 2n in the iteration sequence s(0)=n, s(k+1) = s(k) + (-1)^k*d(s(k)), where d(n) is the number of divisors of n (A000005).

n	a(n)
1	3
2	93
3	273
4	1617
5	684
6	3993
7	58695
8	91355
9	572793
10	167055
11	441519
12	13991016
13	2337513
14	20225991
15	48163788
16	20625997
17	148789675
18	470944675
19	626064036
20	506112555
21	963071088
22	494359089
23	3252701700
24	3972446520
25	4515893681
26	3472027000
27	9096968436

[3, 93, 273, 1617, 684, 3993, 58695, 91355, 572793, 167055, 441519, 13991016, 2337513, 20225991, 48163788, 20625997, 148789675, 470944675, 626064036, 506112555, 963071088, 494359089, 3252701700, 3972446520, 4515893681, 3472027000, 9096968436]

cp's OEIS Frontend

A288070 a(n) is the least number that enters a cycle of length 2n in the iteration sequence s(0)=n, s(k+1) = s(k) + (-1)^k*d(s(k)), where d(n) is the number of divisors of n (A000005).

Table of values

List of values