

A102489


Take the decimal representation of n and read it as if it were written in hexadecimal.


13



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
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OFFSET

0,3


COMMENTS

List of numbers in base16 representation that can be written with decimal digits.
Early in the sequence there are blocks recurring as a(n) = a(n10)+16, but this pattern starts to fail when we reach 160, 161, ... with hexrepresentations 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 binarycoded 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 BenGurion, Aug 28 2019


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..9999
Eric Weisstein's World of Mathematics, Hexadecimal


FORMULA

a(n)  a(n1) = (2*16^A122840(n) + 3)/5.  Robert Israel, Aug 30 2015


EXAMPLE

10 in decimal is 16 in base 16, so a(10)=16.


MAPLE

o10:= n > min(padic:ordp(n, 2), padic:ordp(n, 5)):
d:= [0, seq((2*16^o10(n)+3)/5, n=1..1000)]:
ListTools:PartialSums(d); # Robert Israel, Aug 30 2015


MATHEMATICA

Table[FromDigits[IntegerDigits[n], 16], {n, 0, 70}] (* Ivan Neretin, Aug 12 2015 *)


PROG

(Haskell)
import Data.Maybe (fromJust, mapMaybe)
a102489 n = a102489_list !! (n1)
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'
 Reinhard Zumkeller, Jul 06 2012


CROSSREFS

Complement of A102490; A102487, A102491, A102493, A122840.
Cf. A090725 (the subsequence of primes).
Sequence in context: A032581 A062504 A305458 * A004838 A032998 A032344
Adjacent sequences: A102486 A102487 A102488 * A102490 A102491 A102492


KEYWORD

nonn,base


AUTHOR

Reinhard Zumkeller, Jan 12 2005


EXTENSIONS

Edited by N. J. A. Sloane, Feb 08 2014 (changed definition, moved old definition to comment, changed offset and bfile).


STATUS

approved



