A004167 Powers of 3 written backwards.

1, 3, 9, 72, 18, 342, 927, 7812, 1656, 38691, 94095, 741771, 144135, 3234951, 9692874, 70984341, 12764034, 361041921, 984024783, 7641622611, 1044876843, 30235306401, 90695018313, 72887134149, 184635924282, 344906882748, 9238285681452, 7894847955267

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy

Comments

From a(2) onwards, all terms are divisible by 9. - Alonso del Arte, Apr 04 2014

Examples

			a(5) = 342 since 3^5 = 243.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..1000

Crossrefs

The following are parallel families: A000079 (2^n), A004094 (2^n reversed), A028909 (2^n sorted up), A028910 (2^n sorted down), A036447 (double and reverse), A057615 (double and sort up), A263451 (double and sort down); A000244 (3^n), A004167 (3^n reversed), A321540 (3^n sorted up), A321539 (3^n sorted down), A163632 (triple and reverse), A321542 (triple and sort up), A321541 (triple and sort down).

Programs

Maple

a:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||(3^n)):
seq(a(n), n=0..50);  # Alois P. Heinz, Apr 09 2015

Mathematica

Table[FromDigits[Reverse[IntegerDigits[3^n]]], {n, 0, 26}] (* Alonso del Arte, Apr 04 2014 *)

Python

def A004167(n):
    return int(str(3**n)[::-1]) # Chai Wah Wu, Feb 19 2021

Formula

a(n) = A004086(A000244(n)). - Michel Marcus, Apr 05 2014

Extensions

More terms from Eric M. Schmidt, Apr 04 2014