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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 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.)