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A037383
Numbers k such that every base-3 digit of k is a base-7 digit of k.
7
1, 2, 13, 51, 63, 67, 68, 79, 84, 91, 99, 105, 134, 205, 211, 246, 252, 345, 351, 352, 354, 355, 357, 358, 359, 360, 361, 362, 363, 364, 366, 373, 380, 387, 394, 401, 406, 441, 442, 443, 444, 445, 446, 447, 448, 449, 454, 455, 457
OFFSET
1,2
LINKS
MATHEMATICA
Select[Range[500], Complement[Union[IntegerDigits[#, 3]], Union[IntegerDigits[#, 7]]]=={}&] (* Harvey P. Dale, Jan 28 2024 *)
PROG
(Haskell)
import Data.List ((\\), nub)
a037383 n = a037383_list !! (n-1)
a037383_list = filter f [1..] where
f x = null $ nub (ds 3 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
(PARI) upto(N) = my(s7); [n|n<-[1..N], setunion(Set(digits(n, 3)), s7=Set(digits(n, 7)))==s7]; \\ Ruud H.G. van Tol, May 09 2024
KEYWORD
nonn,base
STATUS
approved