%I #9 Feb 16 2025 08:32:55

%S 10,11,12,13,14,15,16,17,18,19,30,31,32,33,34,35,36,37,38,39,50,51,52,

%T 53,54,55,56,57,58,59,70,71,72,73,74,75,76,77,78,79,90,91,92,93,94,95,

%U 96,97,98,99,110,111,112,113,114,115,116,117,118,119,130,131,132,133

%N Numbers in base-20 representation that cannot be written with decimal digits.

%H Reinhard Zumkeller, <a href="/A102492/b102492.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Vigesimal.html">Vigesimal</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Vigesimal">Vigesimal</a>

%e 112 = 5*20^1 + 12*20^0 = '5C', therefore 112 is a term.

%t Select[Range[150],Max[IntegerDigits[#,20]]>9&] (* _Harvey P. Dale_, Mar 27 2021 *)

%o (Haskell)

%o import Data.List (unfoldr)

%o a102492 n = a102492_list !! (n-1)

%o a102492_list = filter (any (> 9) . unfoldr

%o (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 20)) [0..]

%o -- _Reinhard Zumkeller_, Jun 27 2013

%Y Complement of A102491; A102488, A102490, A102494.

%K nonn,base,changed

%O 1,1

%A _Reinhard Zumkeller_, Jan 12 2005