A171132 The smallest exponent k such that the digit n appears at two adjacent places in the decimal representation of 2^k.

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

Offset

1,1

References

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

Links

Table of n, a(n) for n=1..10.

Theo Kempermann, Zahlentheoretische Kostproben, Harri Deutsch, 2. aktualisierte Auflage 2005

Example

n=0: 2^53 = 9007199254740992, digit 0 duplicated at 9(00)7199254..
n=1: 2^40 = 1099511627776, digit 1 duplicated at 10995(11)627776..
n=2: 2^43 = 8796093022208, digit 2 duplicated even twice
n=3: 2^25 = 33554432, digit 3 duplicated at (33)554432
n=4: 2^18 = 262144
n=5: 2^16 = 65536
n=6: 2^46 = 70368744177664
n=7: 2^24 = 16777216
n=8: 2^19 = 524288
n=9: 2^33 = 8589934592

Crossrefs

Cf. A000079, A018802.

Sequence in context: A033373 A289237 A319904 * A259091 A104936 A262908

Adjacent sequences: A171129 A171130 A171131 * A171133 A171134 A171135

Keyword

nonn,fini,full,base

Author

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

Extensions

Definition simplified, keyword:base,full added - R. J. Mathar, Dec 07 2009

Status

approved