A007379 - OEIS

%I M0973 #20 Aug 28 2016 18:23:35

%S 0,2,4,5,8,12,7,24,16,10,36,13,20,44,15,56,32,18,68,21,48,76,23,88,28,

%T 26,100,29,96,108,31,120,64,34,132,37,40,140,39,152,144,42,164,45,52,

%U 172,47,184,80,50,196,53,176,204,55,216,60,58,228,61,224,236,63,248

%N Earliest sequence with a(a(n)) = 4n.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H T. D. Noe, <a href="/A007379/b007379.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Aa#aan">Index entries for sequences of the a(a(n)) = 2n family</a>

%F a(8n)=4*a(2n), a(8n+1)=8n+2, a(8n+2)=32n+4, a(8n+3)=8n+5, a(8n+4)=4*a(2n+1), a(8n+5)=32n+12, a(8n+6)=8n+7, a(8n+7)=32n+24

%t a[n_] := a[n] = Which[ Mod[n, 8] == 0, 4*a[n/4], Mod[n, 8] == 1, n+1, Mod[n, 8] == 2, 4*(n-2)+4, Mod[n, 8] == 3, n+2, Mod[n, 8] == 4, 4*a[(n-4)/4+1], Mod[n, 8] == 5, 4*(n-5) + 12, Mod[n, 8] == 6, n+1, True, 4*(n-7)+24]; a[0] = 0; Table[ a[n], {n, 0, 63}] (* _Jean-François Alcover_, Sep 24 2012 *)

%Y Cf. A002516, A002517.

%K nonn,nice

%O 0,2

%A _Colin Mallows_, _N. J. A. Sloane_, _Mira Bernstein_

%E Formula and more terms from _Henry Bottomley_, Apr 27 2000