A102260 - OEIS

%I #14 Jun 15 2021 11:02:12

%S 5,10,20,40,80,160,2120,4240,8480,168160,212162120,4242124240,

%T 8484248480,16816848168160,2121621216816212162120,

%U 424212424212162124242124240,8484248484242124248484248480

%N Begin with 5, multiply each digit by 2, keeping the memory of the groupings of the preceding digits.

%F Apply the rule "d*2", beginning with 5

%e Read a(5)=80 which produces a(6)=160 because 8*2=16 and 0*2=0.

%e Now read a(6)=160 which produces a(7)=2120 because 1*2=2, 6*2=12 and 0*2=0.

%e Read a(10)=168160 which produces the digits of a(11)=212162 AND the first three digits of a(12)=1204242 because 1*2=2, 6*2=12, 8*2=16, 1*2=2 AND 6*2=12 and 0*2=0

%t Flatten[ NestList[ Function[x, FromDigits[ Flatten[ IntegerDigits[2IntegerDigits[ x]]] ]], 5, 16]] (* _Robert G. Wilson v_, Feb 21 2005 *)

%K base,easy,nonn

%O 1,1

%A _Alexandre Wajnberg_ and _Eric Angelini_, Feb 19 2005

%E More terms from _Robert G. Wilson v_, Feb 21 2005

%E Edited by _N. J. A. Sloane_, Sep 06 2008 at the suggestion of _R. J. Mathar_