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A037389
Every base 4 digit of k is a base 7 digit of k.
6
1, 2, 3, 9, 52, 84, 85, 86, 87, 105, 106, 170, 191, 255, 345, 352, 357, 358, 360, 361, 362, 366, 368, 369, 381, 394, 406, 409, 410, 415, 422, 444, 462, 479, 486, 492, 496, 497, 501, 503, 504, 505, 506, 507, 509, 510, 511, 553, 597
OFFSET
1,2
LINKS
MATHEMATICA
Select[Range[600], Complement[IntegerDigits[#, 4], IntegerDigits[#, 7]]=={}&] (* Harvey P. Dale, Jan 25 2024 *)
PROG
(Haskell)
import Data.List ((\\), nub)
a037389 n = a037389_list !! (n-1)
a037389_list = filter f [1..] where
f x = null $ nub (ds 4 x) \\ nub (ds 7 x)
ds b x = if x > 0 then d : ds b x' else [] where (x', d) = divMod x b
-- Reinhard Zumkeller, May 30 2013
CROSSREFS
KEYWORD
nonn,base
STATUS
approved