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A264725
Numbers n such that the concatenation of the first n digits of the digital expansion of 1/137 is prime.
0
3, 11, 371, 1123, 8203, 11899, 16019
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.
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 * A374558 A088579 A344946
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