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A037389
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Every base 4 digit of k is a base 7 digit of k.
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6
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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
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listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[600], Complement[IntegerDigits[#, 4], IntegerDigits[#, 7]]=={}&] (* Harvey P. Dale, Jan 25 2024 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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