cp's OEIS Frontend

A215830 Numbers k such that 2^k contains each decimal digit at least twice.

%I A215830 #26 Nov 12 2019 12:50:43
%S A215830 88,104,113,114,116,117,118,119,120,125,126,131,133,134,136,140,141,
%T A215830 142,144,145,146,147,148,150,155,156,157,159,160,161,162,163,164,165,
%U A215830 166,170,171,172,175,177,178,179,180,181,182,185,186,187,188,189,190,191,192
%N A215830 Numbers k such that 2^k contains each decimal digit at least twice.
%C A215830 A subsequence of A130694.
%C A215830 Motivated by J. Merickel's question about the least power of 2 in which all digits 0-9 occur a prime number of times. The first 4 terms of this sequence are all such that this is the case for all but one digit; see Examples.
%C A215830 Beyond 184, the numbers 195-197 and 229 are the only exponents < 10^4 which are not in this sequence. Is 229 the largest such number?
%H A215830 J. Merickel, <a href="http://groups.yahoo.com/group/primenumbers/message/24399">Are these new questions?</a>, Yahoo! group "primenumbers", Aug 24 2012.
%H A215830 James Merickel, <a href="/A215830/a215830.txt">Are these new questions?</a>, message 24399 in primenumbers Yahoo group, Aug 24, 2012.
%e A215830 Digit counts for 2^n:
%e A215830 .
%e A215830   n\d| 0  1  2  3  4  5  6  7  8  9
%e A215830   ---+-----------------------------
%e A215830    88| 5  2  2  2  3  3  2  2  4* 2
%e A215830   104| 5  3  6* 2  3  2  5  2  2  2
%e A215830   113| 5  3  3  2  3  5  4* 3  2  5
%e A215830   114| 3  7  2  5  4* 2  2  2  5  3
%e A215830 .
%e A215830 *nonprime counts
%o A215830 (PARI) is_A215830(n)={my(c=vector(10),N=[1<<n,0]);while(N=divrem(N[1],10),c[N[2]+1]++);vecmin(c)>1}
%K A215830 nonn,base
%O A215830 1,1
%A A215830 _M. F. Hasler_, Aug 25 2012