A036447 Double and reverse digits.

1, 2, 4, 8, 61, 221, 244, 884, 8671, 24371, 24784, 86594, 881371, 2472671, 2435494, 8890784, 86518771, 245730371, 247064194, 883821494, 8892467671, 24353948771, 24579870784, 86514795194, 883095920371, 2470481916671, 2433383690494

Offset

0,2

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Nick Hobson, Python program for this sequence

Formula

a(n+1) = A004093(a(n)). - Reinhard Zumkeller, Feb 09 2012

Conjecture: a(n)^(1/n) tends to sqrt(10). - Vaclav Kotesovec, Jan 03 2020

Mathematica

NestList[ FromDigits[ Reverse[ IntegerDigits[ 2# ] ] ] &, 1, 27 ]
NestList[IntegerReverse[2#]&, 1, 30] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 18 2017 *)

Prog

(Haskell)
a036447 n = a036447_list !! n
a036447_list = iterate a004093 1  -- Reinhard Zumkeller, Feb 09 2012

Crossrefs

Cf. A004086, A004093.

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).

Cf. A132064, A045539, A132078, A132114, A132113, A133361.

Sequence in context: A004094 A028910 A018482 * A371966 A263451 A339951

Adjacent sequences: A036444 A036445 A036446 * A036448 A036449 A036450

Keyword

nonn,base,easy,nice

Author

Rodolfo Kurchan

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Mar 31 2000

Status

approved