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A102489
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Take the decimal representation of n and read it as if it were written in hexadecimal.
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14
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 112
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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COMMENTS
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List of numbers in base-16 representation that can be written with decimal digits.
Early in the sequence there are blocks recurring as a(n) = a(n-10)+16, but this pattern starts to fail when we reach 160, 161, ... with hex-representations A0, A1, ... which cannot be written with decimal digits. - Rick L. Shepherd, Jun 08 2012
Binary Coded Decimal (BCD) codes, common in electronics, when interpreted as plain binary-coded integers. For example, number 39 is BCD coded in two nibbles as 0011 1001 which is the binary expansion of 57; hence, taking into account the offset, a(1+39) = 57. - Stanislav Sykora, Jun 09 2012
Integers that avoid letters in their hexadecimal expansion. - Eliora Ben-Gurion, Aug 28 2019
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LINKS
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FORMULA
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EXAMPLE
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10 in decimal is 16 in base 16, so a(10)=16.
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MAPLE
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o10:= n -> min(padic:-ordp(n, 2), padic:-ordp(n, 5)):
d:= [0, seq((2*16^o10(n)+3)/5, n=1..1000)]:
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MATHEMATICA
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Table[FromDigits[IntegerDigits[n], 16], {n, 0, 70}] (* Ivan Neretin, Aug 12 2015 *)
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PROG
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(Haskell)
import Data.Maybe (fromJust, mapMaybe)
a102489 n = a102489_list !! (n-1)
a102489_list = mapMaybe dhex [0..] where
dhex 0 = Just 0
dhex x | d > 9 || y == Nothing = Nothing
| otherwise = Just $ 16 * fromJust y + d
where (x', d) = divMod x 16; y = dhex x'
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CROSSREFS
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Cf. A090725 (the subsequence of primes).
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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Edited by N. J. A. Sloane, Feb 08 2014 (changed definition, moved old definition to comment, changed offset and b-file).
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STATUS
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approved
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