A100660 Composite numbers whose prime factors have different digital roots.

6, 10, 14, 15, 21, 26, 30, 33, 34, 35, 38, 39, 42, 46, 51, 55, 57, 62, 65, 69, 70, 74, 77, 78, 82, 85, 86, 87, 91, 93, 95, 102, 105, 106, 111, 114, 118, 119, 122, 123, 129, 130, 133, 134, 138, 141, 142, 143, 145, 146, 155, 158, 159, 161, 165, 170, 177, 178, 182, 183

Offset

1,1

Links

Table of n, a(n) for n=1..60.

Example

399=3*7*19. digital roots = 3,7,1 all different.

Prog

(PARI) nsamedr2(n) = { local(j); for(j=2, n, if(!isprime(j)&issamedr2(j), print1(j", ")) ) } issamedr2(n) = { local(f, a, ln, x, y, dr); f=0; a=ifactor(n); ln=length(a); for(x=1, ln-1, for(y=x+1, ln, if(droot(a[x])==droot(a[y]), return(0)); if(droot(a[x])<>droot(a[y]), f=1, f=0))); if(f==1&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)) } ifactor(n) = \The vector of integer factors of n with multiplicity { local(f, j, k, flist); flist=[]; f=Vec(factor(n)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }

Crossrefs

Sequence in context: A338905 A093772 A046400 * A088709 A225706 A063078

Adjacent sequences: A100657 A100658 A100659 * A100661 A100662 A100663

Keyword

base,easy,nonn

Author

Cino Hilliard, Jan 02 2005

Status

approved