A002518 - OEIS

%I #15 Aug 28 2016 18:23:33

%S 0,2,5,4,15,10,7,30,9,40,25,12,55,14,65,20,17,80,19,90,75,22,105,24,

%T 115,50,27,130,29,140,35,32,155,34,165,150,37,180,39,190,45,42,205,44,

%U 215,200,47,230,49,240,125,52,255,54,265,60,57,280,59,290,275,62,305

%N Earliest sequence with a(a(n))=5n.

%H T. D. Noe, <a href="/A002518/b002518.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(5n)=5*a(n), a(5n+1)=5n+2, a(5n+2)=25n+5, a(5n+3)=5n+4, a(5n+4)=25n+15

%t a[n_] := a[n] = Which[ Mod[n, 5] == 0, 5*a[n/5], Mod[n, 5] == 1, n+1, Mod[n, 5] == 2, 5*(n-2)+5, Mod[n, 5] == 3, n+1, True, 5*(n-4)+15]; a[0] = 0; Table[ a[n], {n, 0, 62}] (* _Jean-François Alcover_, Sep 24 2012 *)

%Y Cf. A002516, A002517, A007379.

%K nonn,nice

%O 0,2

%A _Colin Mallows_

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