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 A243972 Least number k such that 2^k contains exactly n identical digits. 3
 1, 16, 22, 23, 53, 70, 74, 93, 122, 147, 156, 167, 168, 222, 214, 221, 283, 315, 311, 312, 313, 314, 426, 466, 427, 474, 439, 563, 630, 576, 554, 575, 626, 627, 793, 722, 809, 766, 861, 889, 925, 893, 989, 890, 1077, 891, 983, 892, 1130, 1128, 1135, 1134, 1217, 1129, 1238 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The terms are not all unique: thus a(491) = a(497) = 14705. - Robert Israel, May 26 2017 LINKS Robert Israel, Table of n, a(n) for n = 1..1000 EXAMPLE 2**22 = 4194304 contains exactly 3 of the same digit (4). Since 22 is the smallest power of 2 to have this, a(3) = 22. MAPLE N:= 100: # To get a(1)..a(N) Agenda:= {\$1..N}: for n from 1 while nops(Agenda) > 0 do   S:= convert(2^n, base, 10);   V:= Vector(10);   for s in S do V[s+1]:= V[s+1]+1 od:   T:= convert(V, set) intersect Agenda;   for t in T do A[t]:= n od:   Agenda:= Agenda minus T; od: seq(A[i], i=1..N); # Robert Israel, May 26 2017 PROG (Python) def b(): ..n = 1 ..k = 1 ..while k < 50000: ....st = str(2**k) ....if len(st) >= n: ......for a in range(10): ........count = 0 ........for i in range(len(st)): ..........if st[i] == str(a): ............count += 1 ........if count == n: ..........print(k, end=', ') ..........n += 1 ..........k = 0 ..........break ......k += 1 ....else: ......k += 1 b() CROSSREFS Cf. A000079, A243975. Sequence in context: A123662 A065778 A305944 * A091118 A294125 A064804 Adjacent sequences:  A243969 A243970 A243971 * A243973 A243974 A243975 KEYWORD nonn,base AUTHOR Derek Orr, Jun 16 2014 STATUS approved

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Last modified January 19 14:53 EST 2020. Contains 331049 sequences. (Running on oeis4.)