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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
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, ...}.
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: A372293 A288452 A338316 * A138217 A074775 A356845
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Jul 25 2011
EXTENSIONS
First term corrected by Jaroslav Krizek, Jul 27 2011
STATUS
approved