A008454 -id:A008454 - cp's OEIS frontend

A257580 Continued square root map applied to tenth powers: 1, 2^10, 3^10, 4^10, ...

6, 0, 5, 1, 8, 1, 3, 3, 2, 9, 5, 2, 1, 5, 2, 6, 6, 0, 2, 1, 0, 4, 7, 3, 0, 8, 4, 4, 8, 1, 2, 9, 3, 3, 8, 3, 7, 4, 1, 4, 6, 8, 8, 3, 5, 3, 2, 2, 7, 8, 6, 3, 7, 0, 9, 9, 2, 9, 9, 5, 0, 0, 0, 2, 7, 7, 2, 9, 8, 6, 5, 7, 3, 5, 3, 2, 1, 6, 4, 0, 7, 6, 2, 8, 2, 0, 0

Offset: 1

N. J. A. Sloane, May 02 2015

The continued square root map applied to a sequence b(1), b(2), b(3), ... produces the decimal number

sqrt(b(1)+sqrt(b(2)+sqrt(b(3)+sqrt(b(4)+...)))).

			6.0518133295215266021047308...

Hiroaki Yamanouchi, Table of n, a(n) for n = 1..1000
Herman P. Robinson, The CSR Function, Popular Computing (Calabasas, CA), Vol. 4 (No. 35, Feb 1976), pages PC35-3 to PC35-4. Annotated and scanned copy.

Cf. A008454 (tenth powers).

a(27)-a(87) from Hiroaki Yamanouchi, May 03 2015

A320522 Numbers k such that k^10 divides 10^k.

Original entry on oeis.org

1, 10, 20, 25, 40, 50, 64, 80, 100, 125, 128, 160, 200, 250, 256, 320, 400, 500, 512, 625, 640, 800, 1000, 1024, 1250, 1280, 1600, 2000, 2048, 2500, 2560, 3125, 3200, 4000, 4096, 5000, 5120, 6250, 6400, 8000, 8192, 10000, 10240, 12500, 12800, 15625, 16000

Offset: 1

Kritsada Moomuang, Oct 14 2018

nonn

The sequence consists of the numbers of the form 2^i*5^j (A003592) except for {2, 4, 5, 8, 16, 32}. - Giovanni Resta, Nov 13 2018

			20 is in the sequence because 20^10 divides 10^20.
5 is not in the sequence because 5^10 does not divide 10^5.

Subsequence of A003592 (numbers of the form 2^i*5^j).

Cf. A008454 (n^10), A011557 (10^n),

Filtered([1..16000],k->PowerMod(10,k,k^10)=0); # Muniru A Asiru, Oct 16 2018

Select[Union@ Flatten@ Table[2^a * 5^b, {a, 0, Log[2, #/(1)]}, {b, 0, Log[5, #/(2^a)]}] &[10^5], PowerMod[10, #, #^10] == 0 &] (* Michael De Vlieger, Oct 15 2018 *)
m = 10^5; DeleteCases[Union @@ Table[2^a*5^b, {a, 0, Log2@ m}, {b, Boole[0 < a < 6], Log[5, m/2^a]}], 5] (* Giovanni Resta, Nov 13 2018 *)

isok(n) = Mod(10, n^10)^n == 0; \\ Michel Marcus, Oct 14 2018

cp's OEIS Frontend

A257580 Continued square root map applied to tenth powers: 1, 2^10, 3^10, 4^10, ...

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Extensions