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!)
A100658 Composite numbers with at least 2 factors that have different digital roots. 1
6, 10, 12, 14, 15, 18, 20, 21, 24, 26, 28, 30, 33, 34, 35, 36, 38, 39, 40, 42, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 60, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 85, 86, 87, 90, 91, 92, 93, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
PROG
(PARI) nsamedr(n) = { local(j); for(j=2, n, if(!isprime(j)&!issamedr(j), print1(j", ")) ) } issamedr(n) = { local(f, a, ln, x); f=0; a=ifactor(n); ln=length(a); for(x=1, ln-1, if(droot(a[x])<>droot(a[x+1]), f=1; break)); if(f==0&ln>1, return(1), return(0)) } droot(n) = \ the digital root of a number. { local(x); x= n%9; if(x>0, return(x), return(9)) }
CROSSREFS
Sequence in context: A340749 A296205 A325281 * A182301 A069059 A273157
KEYWORD
base,easy,nonn
AUTHOR
Cino Hilliard, Jan 02 2005
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 June 25 13:13 EDT 2024. Contains 373705 sequences. (Running on oeis4.)