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Numbers whose decimal expansion contains only 0's and 2's.
14

%I #34 Oct 26 2024 14:45:34

%S 0,2,20,22,200,202,220,222,2000,2002,2020,2022,2200,2202,2220,2222,

%T 20000,20002,20020,20022,20200,20202,20220,20222,22000,22002,22020,

%U 22022,22200,22202,22220,22222,200000,200002,200020,200022,200200,200202,200220,200222

%N Numbers whose decimal expansion contains only 0's and 2's.

%H Reinhard Zumkeller, <a href="/A169965/b169965.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>

%F a(n+1) = Sum_{k>=0} A030308(n,k)*A093136(k+1). - _Philippe Deléham_, Oct 16 2011

%F a(n) = 2 * A007088(n-1).

%t Map[FromDigits,Tuples[{0,2},6]] (* _Paolo Xausa_, Oct 30 2023 *)

%o (PARI) print1(0);for(d=1,5,for(n=2^(d-1),2^d-1,print1(", ");forstep(i=d-1,0,-1,print1((n>>i)%2*2)))) \\ _Charles R Greathouse IV_, Nov 16 2011

%o (PARI) lista(N) = vector(N, i, fromdigits(binary(i-1)*2)); \\ _Ruud H.G. van Tol_, Oct 26 2024

%o (Haskell)

%o a169965 n = a169965_list !! (n-1)

%o a169965_list = map (* 2) a007088_list

%o -- _Reinhard Zumkeller_, Jan 10 2012

%Y Cf. A007088, A014263, A169964, A169966, A169967.

%Y Cf. A078241, A204093, A204094, A204095, A097256.

%K nonn,base,easy

%O 1,2

%A _N. J. A. Sloane_, Aug 07 2010