login
a(1) = 1, a(n) = number obtained by replacing each digit of a(n-1) with three times its value.
7

%I #11 Mar 31 2017 22:13:29

%S 1,3,9,27,621,1863,324189,961232427,2718369612621,6213249182718361863,

%T 1863961227324621324918324189,

%U 32418927183662196121863961227324961232427,961232427621324918186327183632418927183662196122718369612621

%N a(1) = 1, a(n) = number obtained by replacing each digit of a(n-1) with three times its value.

%C Number of digits of each term in this sequence is sequence A000930. - _Dmitry Kamenetsky_, Jan 17 2009

%C Each of the subsequences a(5n), a(5n-1), ..., a(5n-4) seem to converge to a different fixed point of the operation (if the terms are seen as sequences of digits). - _M. F. Hasler_, Jun 24 2016

%C a(20) has 1278 decimal digits. - _Michael De Vlieger_, Jun 24 2016

%H Michael De Vlieger, <a href="/A061582/b061582.txt">Table of n, a(n) for n = 1..20</a>

%t NestList[FromDigits@ Flatten@ Map[IntegerDigits, 3 IntegerDigits@ #] &, 1, 12] (* _Michael De Vlieger_, Jun 24 2016 *)

%o (PARI) A061582(n=2,a=1,m=3)={while(n--,a=eval(concat(apply(t->Str(t),digits(a)*m))));a} \\ If only the 2nd argument is given, then the operation is applied once to that argument. - _M. F. Hasler_, Jun 24 2016

%Y Cf. A061581 - A061587.

%K nonn,base,easy

%O 1,2

%A _Amarnath Murthy_, May 13 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), May 14 2001