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A004647 Powers of 2 written in base 8.

%I A004647 #35 Sep 08 2022 08:44:33
%S A004647 1,2,4,10,20,40,100,200,400,1000,2000,4000,10000,20000,40000,100000,
%T A004647 200000,400000,1000000,2000000,4000000,10000000,20000000,40000000,
%U A004647 100000000,200000000,400000000,1000000000
%N A004647 Powers of 2 written in base 8.
%C A004647 Or, numbers of form 10^n, 2*10^n, 4*10^n.
%C A004647 Or, numbers n such that the digits of n^3 are decreasing. - _Dmitry Kamenetsky_, Jun 15 2006
%H A004647 Vincenzo Librandi, <a href="/A004647/b004647.txt">Table of n, a(n) for n = 0..1000</a>
%H A004647 Thomas Harriot, <a href="http://echo.mpiwg-berlin.mpg.de/MPIWG:5PYT50NY">Manuscript 6782</a>, <a href="http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?tocMode=thumbs&amp;url=/mpiwg/online/permanent/library/HSPGZ0AE/&amp;viewMode=image&amp;tocPN=1&amp;searchPN=1&amp;characterNormalization=reg&amp;query=&amp;queryType=">p. 1</a>, c. 1599.
%H A004647 D. Panario, M. Sahin, and Q. Wang, <a href="http://www.emis.de/journals/INTEGERS/papers/n78/n78.Abstract.html">A family of Fibonacci-like conditional sequences</a>, INTEGERS, Vol. 13, 2013, #A78.
%H A004647 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,10).
%F A004647 a(0)=1, a(1)=2, a(2)=4, a(n)=10*a(n-3). - _Harvey P. Dale_, Aug 16 2012
%F A004647 G.f.: (1 + 2*x + 4*x^2)/(1 - 10*x^3 ). - _R. J. Mathar_, Mar 13 2015
%t A004647 Table[FromDigits[IntegerDigits[2^n,8]],{n,0,30}] (* or *) LinearRecurrence[ {0,0,10},{1,2,4},30] (* _Harvey P. Dale_, Aug 16 2012 *)
%o A004647 (PARI) a(n)=2^(n%3)*10^(n\3) \\ _Charles R Greathouse IV_, Oct 22 2014
%o A004647 (Magma) [Seqint(Intseq(2^n, 8)): n in [0..30]]; // _G. C. Greubel_, Sep 10 2018
%o A004647 (Python)
%o A004647 def A004647(n): return int(oct(2**n)[2:]) # _Chai Wah Wu_, May 23 2022
%K A004647 nonn,base,easy
%O A004647 0,2
%A A004647 _N. J. A. Sloane_