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

1,1

Links

Table of n, a(n) for n=1..67.

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

Adjacent sequences: A100655 A100656 A100657 * A100659 A100660 A100661

Keyword

base,easy,nonn

Author

Cino Hilliard, Jan 02 2005

Status

approved