login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A236653 Positive integers n such that n^3 divided by the digital root of n is a cube. 2
1, 8, 10, 19, 26, 28, 37, 44, 46, 55, 62, 64, 73, 80, 82, 91, 98, 100, 109, 116, 118, 127, 134, 136, 145, 152, 154, 163, 170, 172, 181, 188, 190, 199, 206, 208, 217, 224, 226, 235, 242, 244, 253, 260, 262, 271, 278, 280, 289, 296, 298, 307, 314, 316, 325 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).

FORMULA

a(n) = a(n-1)+a(n-3)-a(n-4).

G.f.: x*(8*x^3+2*x^2+7*x+1) / ((x-1)^2*(x^2+x+1)).

EXAMPLE

26 is in the sequence because the digital root of 26 is 8, and 26^3/8 = 2197 = 13^2.

MATHEMATICA

LinearRecurrence[{1, 0, 1, -1}, {1, 8, 10, 19}, 60] (* Harvey P. Dale, Sep 15 2019 *)

PROG

(PARI) s=[]; for(n=1, 400, d=(n-1)%9+1; if(n^3%d==0 && ispower(n^3\d, 3), s=concat(s, n))); s

(PARI) Vec(x*(8*x^3+2*x^2+7*x+1)/((x-1)^2*(x^2+x+1)) + O(x^100))

CROSSREFS

Cf. A010888, A236652.

Sequence in context: A153382 A157911 A090097 * A257274 A022322 A302637

Adjacent sequences: A236650 A236651 A236652 * A236654 A236655 A236656

KEYWORD

nonn,base,easy

AUTHOR

Colin Barker, Jan 29 2014

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 1 14:50 EDT 2023. Contains 361695 sequences. (Running on oeis4.)