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

Author

Amarnath Murthy, May 13 2001

Keywords

• nonn
• base
• easy

Links

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

Crossrefs

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

Programs

Mathematica

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

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