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A235713 Least number k such that 2^k begins with exactly n identical digits. 1
1, 25, 143, 1598, 10627, 194220, 26399, 37811757, 15689797, 1609719151, 42001126081, 42116737194, 2277292670319, 8475536580225, 57483036385216, 1185808703658960, 2800250032195382, 203292337502775829, 294180235677139843, 28666496154250702728 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(8) > 200000. The repeating digits that corresponds to a(n) are {2, 3, 1, 1, 1, 1, 7, 1, 3, 1, 1, 7} respectively.

a(8) > 3*10^7, a(9) = 15689797 (repeating digit is 3). - Lars Blomberg, Jul 02 2014

LINKS

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..100

EXAMPLE

2^25 = 33554432 begins with two identical digits ('33'). Thus a(2) = 25.

PROG

(Python)

def b(n):

..for k in range(1, 2*10**5):

....st = str(2**k)

....count = 0

....if len(st) >= n:

......for i in range(len(st)):

........if st[i] == st[0]:

..........count += 1

........else:

..........break

......if count == n:

........return k

n = 1

while n < 10:

..print(b(n), end=', ')

..n += 1

CROSSREFS

Sequence in context: A147360 A147223 A184057 * A072471 A017042 A100255

Adjacent sequences:  A235710 A235711 A235712 * A235714 A235715 A235716

KEYWORD

nonn,base

AUTHOR

Derek Orr, Jun 13 2014

EXTENSIONS

a(8)-a(12) from Hiroaki Yamanouchi, Jul 13 2014

a(13)-a(20) from Hiroaki Yamanouchi, May 31 2015

STATUS

approved

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Last modified October 21 16:00 EDT 2018. Contains 316424 sequences. (Running on oeis4.)