A087000 Half length of periodic part of decimal expansion of 1/p for those primes having a periodic part of even length.

3, 1, 3, 8, 9, 11, 14, 23, 29, 30, 4, 22, 48, 2, 17, 54, 56, 21, 65, 4, 23, 74, 39, 83, 89, 90, 96, 49, 15, 111, 114, 116, 15, 25, 128, 131, 134, 14, 73, 156, 55, 168, 58, 16, 183, 93, 189, 191, 194, 100, 102, 209, 70, 216, 16, 76, 230, 77, 243, 245, 249, 251

Offset: 1

Author

Reinhard Zumkeller, Jul 29 2003

Keywords

• nonn
• base

Comments

a(n) appears to be the least k such that 10^k+1 is divisible by A028416(n). See A001271. - Michel Marcus, Aug 13 2023

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• Index entries for sequences related to decimal expansion of 1/n.

Crossrefs

Cf. A028416, A002371, A086999, A087001, A087002, A001271, A062397 (10^n+1).

Formula

a(n) = A002371(A049084(A028416(n)))/2.

a(n) = A055642(A086999(n))/2.

a(n) = A055642(A087001(n)) = A055642(A087002(n)).