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A259089
Least k such that 2^k has at least n consecutive 2's in its decimal representation.
7
0, 1, 43, 43, 314, 314, 2354, 8555, 13326, 81784, 279272, 865356, 1727602, 1727602
OFFSET
0,3
LINKS
Popular Computing (Calabasas, CA), Two Tables, Vol. 1, (No. 9, Dec 1973), page PC9-16.
EXAMPLE
a(3)=43 because 2^43 (i.e. 8796093022208) is the smallest power of 2 to contain a run of 3 consecutive twos in its decimal form.
MATHEMATICA
Table[k = 0; While[! SequenceCount[IntegerDigits[2^k], ConstantArray[2, n]] > 0, k++]; k, {n, 10}] (* Robert Price, May 17 2019 *)
PROG
(Python)
def A259089(n):
s, k, k2 = '2'*n, 0, 1
while True:
if s in str(k2):
return k
k += 1
k2 *= 2 # Chai Wah Wu, Jun 19 2015
CROSSREFS
KEYWORD
more,nonn,base
AUTHOR
N. J. A. Sloane, Jun 18 2015
EXTENSIONS
a(7)-a(13) from Chai Wah Wu, Jun 20 2015
Definition corrected by Manfred Scheucher, Jun 23 2015
a(0) prepended by Chai Wah Wu, Jan 28 2020
STATUS
approved