The OEIS is supported by the many generous donors to the OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A306494 Smallest number m such that n*3^m has 2 or more identical adjacent decimal digits. 2
 11, 8, 10, 8, 11, 7, 9, 5, 9, 11, 0, 7, 2, 4, 10, 2, 4, 6, 7, 8, 8, 0, 5, 4, 2, 9, 8, 4, 6, 10, 4, 2, 0, 8, 6, 6, 1, 1, 1, 8, 3, 3, 3, 0, 9, 5, 5, 1, 2, 11, 3, 7, 2, 5, 0, 7, 6, 2, 1, 7, 6, 2, 7, 5, 3, 0, 6, 4, 4, 9, 7, 3, 5, 1, 1, 1, 0, 8, 2, 5, 7, 3, 3, 3, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is smallest m such that 3^m*n is in the sequence A171901 (or -1 if no such m exists). 0 <= a(n) <= 35 for all n > 0. This is proved by showing that for each 0 < n < 10^9, there is a number m <= 35 such that 3^m*n mod 10^9 has adjacent identical digits. If n > 0 and n == 0 mod 10^9, then clearly a(n) = 0. LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 FORMULA a(A171901(n)) = 0. EXAMPLE a(1) = 11 since 3^11 = 177147 has 2 adjacent digits '7' and no smaller power of 3 has adjacent identical digits. Record values: a(1) = 11 a(241) = 12 a(2392) = 14 a(35698) = 15 a(267345) = 16 a(893521) = 17 a(29831625) = 18 a(3232453125) = 19 PROG (Python) def A306494(n):     m, k= 0, n     while True:         s = str(k)         for i in range(1, len(s)):             if s[i] == s[i-1]:                 return m         m += 1         k *= 3 CROSSREFS Cf. A171901, A306305. Sequence in context: A003567 A085688 A164059 * A068974 A244447 A206420 Adjacent sequences:  A306491 A306492 A306493 * A306495 A306496 A306497 KEYWORD nonn,base AUTHOR Chai Wah Wu, Feb 19 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 13 18:03 EDT 2022. Contains 356107 sequences. (Running on oeis4.)