A097254 - OEIS

%I #26 Sep 08 2022 08:45:14

%S 0,7,56,63,448,455,504,511,3584,3591,3640,3647,4032,4039,4088,4095,

%T 28672,28679,28728,28735,29120,29127,29176,29183,32256,32263,32312,

%U 32319,32704,32711,32760,32767,229376,229383,229432,229439,229824

%N Numbers whose set of base 8 digits is {0,7}.

%C n such that there exists a permutation p_1, ..., p_n of 1, ..., n such that i + p_i is a power of 8 for every i.

%H Vincenzo Librandi, <a href="/A097254/b097254.txt">Table of n, a(n) for n = 1..100</a>

%F a(n) = 7*A033045(n-1).

%F a(2n-1) = 8*a(n), a(2n) = 8*a(n)+7.

%t fQ[n_]:=Union@Join[{0,7},IntegerDigits[n,8]]=={0,7};Select[Range[0,300000],fQ] (* _Vincenzo Librandi_, May 25 2012 *)

%t FromDigits[#,8]&/@Tuples[{0,7},6] (* _Harvey P. Dale_, Aug 10 2021 *)

%o (Magma) [n: n in [0..250000] | Set(IntegerToSequence(n, 8)) subset {0, 7}]; // _Vincenzo Librandi_, May 25 2012

%o (Maxima) a[1]:0$ a[n]:=8*a[floor((n+1)/2)]+7*(1+(-1)^n)/2$ makelist(a[n], n, 1, 37); /* _Bruno Berselli_, May 25 2012 */

%o (PARI) a(n) = 7*fromdigits(binary(n-1), 8) \\ _Rémy Sigrist_, Dec 06 2018

%Y Cf. A001196, A005823, A097251-A097262.

%K nonn,base

%O 1,2

%A _Ray Chandler_, Aug 03 2004