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A032925 Numbers whose set of base 4 digits is {1,2}. 7
1, 2, 5, 6, 9, 10, 21, 22, 25, 26, 37, 38, 41, 42, 85, 86, 89, 90, 101, 102, 105, 106, 149, 150, 153, 154, 165, 166, 169, 170, 341, 342, 345, 346, 357, 358, 361, 362, 405, 406, 409, 410, 421, 422, 425, 426, 597, 598, 601, 602, 613 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Intersection of A023705 and A023717; A179888 is the intersection of this sequence and A053754. - Reinhard Zumkeller, Jul 31 2010

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..1000

FORMULA

a(2n) = 4a(n-1) + 2, a(2n+1) = 4a(n) + 1. - Ralf Stephan, Oct 07 2003, corrected R. J. Mathar, Sep 07 2016

MAPLE

A032925 := proc(n)

    option remember;

    if n <= 2 then

        n;

    else

        if type(n, 'even') then

            2+4*procname(n/2-1) ;

        else

            1+4*procname(floor(n/2)) ;

        end if;

    end if;

end proc:

seq(A032925(n), n=1..100) ;  # R. J. Mathar, Sep 07 2016

MATHEMATICA

Flatten[Table[FromDigits[#, 4]&/@Tuples[{1, 2}, n], {n, 5}]] (* Vincenzo Librandi, Jun 05 2012 *)

PROG

(MAGMA) [n: n in [1..1000] | Set(IntegerToSequence(n, 4)) subset {1, 2}]; // Vincenzo Librandi, Jun 05 2012

(Haskell)

import Data.List (transpose)

a032925 n = a032925_list !! (n-1)

a032925_list = 1 : 2 : (concat $ transpose [map (+ 1) fs, map (+ 2) fs])

               where fs = map (* 4) a032925_list

-- Reinhard Zumkeller, Apr 18 2015

CROSSREFS

Cf. A023705, A023717, A179888, A053754.

Sequence in context: A191172 A078632 A122701 * A244749 A166087 A281902

Adjacent sequences:  A032922 A032923 A032924 * A032926 A032927 A032928

KEYWORD

nonn,base,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified May 23 06:42 EDT 2017. Contains 286909 sequences.