A061580 a(1) = 1, a(n)= number obtained by replacing each digit of a(n-1) with four times its value.

1, 4, 16, 424, 16816, 42432424, 1681612816816, 42432424483242432424, 168161281681616321281681612816816, 42432424483242432424424128483242432424483242432424

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..16

Mathematica

NestList[FromDigits@ Flatten@ Map[IntegerDigits, 4*IntegerDigits[#]] &, 1, 9] (* Michael De Vlieger, Feb 25 2023 *)

Crossrefs

Cf. A061581, A061582, A061583, A061584, A061585, A061586, A061587.

Sequence in context: A067211 A156337 A000874 * A037976 A013138 A262546

Adjacent sequences: A061577 A061578 A061579 * A061581 A061582 A061583

Keyword

nonn,base,easy

Author

Amarnath Murthy, May 13 2001

Extensions

More terms from Larry Reeves (larryr(AT)acm.org) and Asher Auel, May 15 2001

a(9) corrected by N. J. A. Sloane, Jan 23 2017 at the suggestion of Carolyn Liao.

a(10) corrected by Sean A. Irvine, Feb 25 2023

Status

approved