login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A118719 Cubes for which the digital root is also a cube. 5
0, 1, 8, 64, 125, 343, 512, 1000, 1331, 2197, 2744, 4096, 4913, 6859, 8000, 10648, 12167, 15625, 17576, 21952, 24389, 29791, 32768, 39304, 42875, 50653, 54872, 64000, 68921, 79507, 85184, 97336, 103823, 117649, 125000, 140608, 148877 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

All cubes have a digital root 1,8 or 9. (except for the number 0) So this sequence contains all cubes with a digital root which is not 9.

This sequence is 0 union A016779 union A016791.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..3000

FORMULA

a(n) = (floor(3*n/2)-2)^3 for n >= 2. - Nathaniel Johnston, May 05 2011

G.f.: x^2*(1+7*x+53*x^2+40*x^3+53*x^4+7*x^5+x^6)/((1+x)^3*(1-x)^4).  a(n) = A001651(n-1)^3 for n>1. - Bruno Berselli, May 05 2011

EXAMPLE

64 is in the sequence because (1) it is a cube and (2) the digital root 1 is also a cube.

PROG

(MAGMA) [0] cat [(6*n+(-1)^n-9)^3 div 64: n in [2..37]];  // Bruno Berselli, May 05 2011

(PARI) a010888(n)=if(n, (n-1)%9+1)

lista(nn) = {for (n=0, nn, if (ispower(a010888(n^3), 3), print1(n^3, ", ")); ); } \\ Michel Marcus, Feb 18 2015

CROSSREFS

Cf. A000578, A010888, A116978.

Sequence in context: A208380 A160428 A074102 * A134739 A116978 A125110

Adjacent sequences:  A118716 A118717 A118718 * A118720 A118721 A118722

KEYWORD

base,easy,nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), May 21 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 19 19:49 EST 2019. Contains 319309 sequences. (Running on oeis4.)