login
A338792
a(n) is the least number k such that 1/prime(k) has repeating decimal expansion of period n.
0
1, 2, 5, 12, 26, 13, 4, 52, 21, 28693, 1128, 2431, 1221, 16, 71954, 11, 7, 153888, 8, 27417323062119920, 496, 14, 9, 223378173194137397198, 5760923, 2403, 149, 134, 10, 452, 47, 406, 71, 19, 27, 20, 37607875619, 150886, 22544062111497849
OFFSET
0,2
FORMULA
a(0) = 1; a(n) = A000720(A007138(n)).
EXAMPLE
1/prime(1) = 1/2 = 0.5 (finite decimal expansion).
1/prime(2) = 1/3 = 0.3(3)... (period 1).
1/prime(5) = 1/11 = 0.09(09)... (period 2).
1/prime(12) = 1/37 = 0.027(027)... (period 3).
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Nov 09 2020
EXTENSIONS
a(19)-a(38) from Daniel Suteu, Nov 09 2020 [using data from A007138 and A234317]
STATUS
approved