

A264725


Numbers n such that the concatenation of the first n digits of the digital expansion of 1/137 is prime.


0




OFFSET

1,1


COMMENTS

No further terms through 5000.
a(n) == 3 mod 8 for all n. If m <> 3 mod 8, then the concatenation of the first m digits is either even or a multiple of 3.  Chai Wah Wu, Nov 24 2015


REFERENCES

Clifford A. Pickover, A Passion for Mathematics, John Wiley & Sons, Inc., 2005, p. 88.


LINKS

Table of n, a(n) for n=1..7.


MATHEMATICA

Select[Range[2000], PrimeQ[FromDigits[PadRight[{}, #, {0, 0, 7, 2, 9, 9, 2, 7}]]]&]


PROG

(Python)
from sympy import isprime
A264725_list, c, n, m, k = [], 3, 7, 29927007, 10**8
for i in range(1, 50):
if isprime(n):
A264725_list.append(c)
c += 8
n = n*k+m # Chai Wah Wu, Nov 24 2015


CROSSREFS

Sequence in context: A097423 A111130 A337415 * A088579 A344946 A006938
Adjacent sequences: A264722 A264723 A264724 * A264726 A264727 A264728


KEYWORD

nonn,base,more


AUTHOR

Harvey P. Dale, Nov 22 2015


EXTENSIONS

a(5)a(7) from Chai Wah Wu, Nov 24 2015


STATUS

approved



