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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 (list; graph; refs; listen; history; text; internal format)
 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: A372293 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

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Last modified August 13 05:48 EDT 2024. Contains 375113 sequences. (Running on oeis4.)