A175557 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

A175557

Prime preperiodic part of the decimal expansion of 1/k as k runs through A065502.

5, 2, 5, 41, 3, 2, 2, 2, 17, 13, 11, 89, 7, 5, 5, 5, 41, 3, 3, 347, 3, 3, 3, 29, 2, 2, 2, 2, 26041, 2, 2, 2, 23, 2, 2, 2, 2, 2, 17, 13, 13, 1201, 11, 11, 107, 919, 89, 7, 7, 7, 7, 7, 7, 61, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 41, 4111, 3

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Primes in A175555 in the order of appearance.

Multiples of 2 or 5 generate a quotient with a preperiodic sequence of digits, for example 1/24 = 0.041666666..., and 41 is the decimal form of the preperiodic part.

The corresponding values of n are: 2, 5, 20, 24, 28, 36, 44, 50, 56, 72, 88, 112, 136, 168, 184, ...

REFERENCES

H. Rademacher and O. Toeplitz, Von Zahlen und Figuren (Springer 1930, reprinted 1968), ch. 19, 'Die periodischen Dezimalbrueche'.

LINKS

Table of n, a(n) for n=1..69.

EXAMPLE

The prime 347 is in the sequence because 1/288 = .00347222222222222222...

The prime 1201 is in the sequence because 1/832 =.001201 923076 923076 ...

MAPLE

for n from 1 do

p := A175555(n) ;

if isprime(p) then