A100658 Composite numbers with at least 2 factors that have different digital roots.

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

Offset: 1

Author

Cino Hilliard, Jan 02 2005

Keywords

• base
• easy
• nonn

Programs

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)) }