A102490 Numbers in base-16 representation that cannot be written with decimal digits.
10, 11, 12, 13, 14, 15, 26, 27, 28, 29, 30, 31, 42, 43, 44, 45, 46, 47, 58, 59, 60, 61, 62, 63, 74, 75, 76, 77, 78, 79, 90, 91, 92, 93, 94, 95, 106, 107, 108, 109, 110, 111, 122, 123, 124, 125, 126, 127, 138, 139, 140, 141, 142, 143, 154, 155, 156, 157, 158, 159, 160
Offset: 1
Examples
42 = 2*16^1 + 10*16^0 = '2A', therefore 42 is a term.
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
- Eric Weisstein's World of Mathematics, Hexadecimal
- Wikipedia, Hexadecimal
Programs
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Haskell
import Data.List (unfoldr) a102490 n = a102490_list !! (n-1) a102490_list = filter (any (> 9) . unfoldr (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 16)) [0..] -- Reinhard Zumkeller, Jun 27 2013
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Mathematica
Select[Range[200],IntegerLength[Max[IntegerDigits[#,16]]]>1&] (* Harvey P. Dale, Jun 12 2020 *)
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Python
def ok(n): return any(hd > '9' for hd in hex(n)[2:]) print(list(filter(ok, range(161)))) # Michael S. Branicky, Oct 11 2021