A061582 a(1) = 1, a(n) = number obtained by replacing each digit of a(n-1) with three times its value.

1, 3, 9, 27, 621, 1863, 324189, 961232427, 2718369612621, 6213249182718361863, 1863961227324621324918324189, 32418927183662196121863961227324961232427, 961232427621324918186327183632418927183662196122718369612621

Offset: 1

Author

Amarnath Murthy, May 13 2001

Keywords

• nonn
• base
• easy

Comments

Number of digits of each term in this sequence is sequence A000930. - Dmitry Kamenetsky, Jan 17 2009

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

a(20) has 1278 decimal digits. - Michael De Vlieger, Jun 24 2016

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..20

Crossrefs

Cf. A061581 - A061587.

Programs

Mathematica

NestList[FromDigits@ Flatten@ Map[IntegerDigits, 3 IntegerDigits@ #] &, 1, 12] (* Michael De Vlieger, Jun 24 2016 *)

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

Extensions

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