A004643 Powers of 2 written in base 4.

1, 2, 10, 20, 100, 200, 1000, 2000, 10000, 20000, 100000, 200000, 1000000, 2000000, 10000000, 20000000, 100000000, 200000000, 1000000000, 2000000000, 10000000000, 20000000000, 100000000000, 200000000000

Offset

0,2

Comments

Also seems to be numbers k such that the digits of k^3 are cubes. - Colin Barker, Apr 21 2017

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,10).

Formula

From Chai Wah Wu, Sep 03 2020: (Start)

a(n) = 10*a(n-2) for n > 1.

G.f.: (-2*x - 1)/(10*x^2 - 1). (End)

a(n) = (3-(-1)^n)/2 * 10^floor(n/2). - Bernard Schott, Sep 17 2020

Mathematica

Table[FromDigits[IntegerDigits[2^n, 4]], {n, 0, 40}] (* Vincenzo Librandi, Jun 07 2013 *)
Table[{1, 2}10^n, {n, 0, 20}]//Flatten (* Harvey P. Dale, Feb 14 2018 *)

Prog

(PARI) for(n=0, 30, print1(fromdigits(digits(2^n, 4)), ", ")) \\ G. C. Greubel, Sep 10 2018
(Magma) [Seqint(Intseq(2^n, 4)): n in [0..30]]; // G. C. Greubel, Sep 10 2018

Crossrefs

Sequence in context: A324474 A294493 A261660 * A284213 A156818 A037422

Adjacent sequences: A004640 A004641 A004642 * A004644 A004645 A004646

Keyword

nonn,base,easy

Author

N. J. A. Sloane

Status

approved