A171132 - OEIS

%I #2 Mar 30 2012 17:40:15

%S 53,40,43,25,18,16,46,24,19,33

%N The smallest exponent k such that the digit n appears at two adjacent places in the decimal representation of 2^k.

%D Helmut Kracke, Mathe-musische Knobelisken, Duemmler Bonn, 2. Auflage 1983

%H Theo Kempermann, <a href="http://www.harri-deutsch.de/verlag/titel/kemperma/s_1692.htm">Zahlentheoretische Kostproben</a>, Harri Deutsch, 2. aktualisierte Auflage 2005

%e n=0: 2^53 = 9007199254740992, digit 0 duplicated at 9(00)7199254..

%e n=1: 2^40 = 1099511627776, digit 1 duplicated at 10995(11)627776..

%e n=2: 2^43 = 8796093022208, digit 2 duplicated even twice

%e n=3: 2^25 = 33554432, digit 3 duplicated at (33)554432

%e n=4: 2^18 = 262144

%e n=5: 2^16 = 65536

%e n=6: 2^46 = 70368744177664

%e n=7: 2^24 = 16777216

%e n=8: 2^19 = 524288

%e n=9: 2^33 = 8589934592

%Y Cf. A000079, A018802.

%K nonn,fini,full,base

%O 1,1

%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Dec 04 2009

%E Definition simplified, keyword:base,full added - _R. J. Mathar_, Dec 07 2009