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Positive numbers k such that every base-2 digit of k is a base-7 digit of k.
8

%I #17 Apr 13 2021 23:01:47

%S 1,7,15,49,50,51,52,53,54,55,56,63,70,77,84,91,99,105,127,148,154,197,

%T 203,246,252,255,295,301,343,344,345,346,347,348,349,350,351,352,353,

%U 354,355,356,357,358,359,360,361,362,363,364

%N Positive numbers k such that every base-2 digit of k is a base-7 digit of k.

%H Reinhard Zumkeller, <a href="/A037376/b037376.txt">Table of n, a(n) for n = 1..10000</a>

%t mtchQ[n_]:=Module[{b7=Union[IntegerDigits[n,7]],b2=Union[IntegerDigits[n,2]]},MemberQ[Partition[b7,Length[b2],1],b2]]

%t Select[Range[400],mtchQ] (* _Harvey P. Dale_, Feb 20 2011 *)

%o (Haskell)

%o import Data.List ((\\), nub)

%o a037376 n = a037376_list !! (n-1)

%o a037376_list = filter f [1..] where

%o f x = null $ nub (ds 2 x) \\ nub (ds 7 x)

%o ds b x = if x > 0 then d : ds b x' else [] where (x', d) = divMod x b

%o -- _Reinhard Zumkeller_, May 30 2013

%Y Cf. A037372, A037373, A037374, A037375, A037377, A037378, A037379.

%K nonn,base

%O 1,2

%A _Clark Kimberling_