A193414 Numbers m such that written in base 2 the structure of digits represents a valley.

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

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

Table of n, a(n) for n=1..59.

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

Cf. A193413 (Valley numbers written in base 10), A193415.

Sequence in context: A143452 A288452 A338316 * A138217 A074775 A356845

Adjacent sequences: A193411 A193412 A193413 * A193415 A193416 A193417

Keyword

nonn,base

Author

Jaroslav Krizek, Jul 25 2011

Extensions

First term corrected by Jaroslav Krizek, Jul 27 2011

Status

approved