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A243150 Least number k > 0 such that 2^k contains an n-digit long substring of the infinite string "0123456789012345678901234567890123456....". 1
1, 7, 28, 106, 391, 992, 1178, 7255, 15975, 67143, 333212, 333212, 1641257 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

By A238448, a(10) <= 244178.

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

2^7 = 128 contains the 2-digit substring "12". Thus a(2) = 7.

PROG

(Python)

def a(n):

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

....for i in range(10):

......s = ''

......for j in range(i, i+n):

........dig=j%10

........s+=str(dig)

......if str(2**k).find(s) > -1:

........return k

n=1

while n < 10:

..print(a(n))

..n+=1

CROSSREFS

Cf. A238448.

Sequence in context: A000416 A000417 A200762 * A026642 A200467 A002042

Adjacent sequences:  A243147 A243148 A243149 * A243151 A243152 A243153

KEYWORD

nonn,more,hard,base

AUTHOR

Derek Orr, May 31 2014

EXTENSIONS

a(10)-a(13) from Hiroaki Yamanouchi, Sep 26 2014

STATUS

approved

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Last modified August 4 18:27 EDT 2020. Contains 336202 sequences. (Running on oeis4.)