

A193414


Numbers m such that written in base 2 the structure of digits represents a valley.


2



1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 23, 25, 27, 29, 31, 33, 35, 39, 47, 49, 51, 55, 57, 59, 61, 63, 65, 67, 71, 79, 95, 97, 99, 103, 111, 113, 115, 119, 121, 123, 125, 127, 129, 131, 135, 143, 159, 191, 193, 195, 199, 207, 223, 225, 227, 231, 239, 241, 243
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OFFSET

1,2


COMMENTS

For n > 1 the structure of digits of numbers written in base 2 represents a valley. The first digit is equal to the last digit (1). The first digits are in nonincreasing order. The last digits are in nondecreasing order. The numbers may have more than one 0 digit. Sequence is infinite.
See A193415: numbers m written in base 2: {1, 11, 101, 111, 1001, 1011, 1101, 1111, ...}.


LINKS



EXAMPLE

Illustration using 67 = 1000011_2:
1 . . . . 1 1
. 0 0 0 0 . .


MATHEMATICA

Select[Range[300], MemberQ[{1, 3}, Length[Split[IntegerDigits[#, 2]]]] &] (* T. D. Noe, Jul 26 2011 *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



