A162422 Numbers with at least 2 different numbers of digits among their prime factors.

22, 26, 33, 34, 38, 39, 44, 46, 51, 52, 55, 57, 58, 62, 65, 66, 68, 69, 74, 76, 77, 78, 82, 85, 86, 87, 88, 91, 92, 93, 94, 95, 99, 102, 104, 106, 110, 111, 114, 115, 116, 117, 118, 119, 122, 123, 124, 129, 130, 132, 133, 134, 136, 138, 141, 142, 145, 146, 148, 152

Offset

1,1

Comments

Complement of A162421. There are no prime numbers in this sequence.

These numbers can also be called factor rough numbers.

Basically, the number of digits of A020639(k) and of A006530(k) must differ to admit k into the sequence.

Links

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

Formula

{k >1: A055642(A020639(k)) <> A055642(A006530(k)) }. - R. J. Mathar, Sep 16 2009

Example

1111 = 11*101 has factors with different digital lengths. Also it is the first occurrence that differs from A084891.

Prog

(PARI) factorrough(m, n) =
{
local(x, a, j, f, ln);
for(x=m, n, f=0; a = ifactor(x); for(j=2, length(a), ln=length(Str(a[j-1])); if(length(Str(a[j]))!=ln, f=1; break); ); if(f, print1(x", ")); );
}

Crossrefs

Cf. A084891, A162457

Sequence in context: A160078 A066059 A084891 * A063940 A046442 A101549

Adjacent sequences: A162419 A162420 A162421 * A162423 A162424 A162425

Keyword

base,nonn

Author

Cino Hilliard, Jul 03 2009

Extensions

Offset set to 1, definition shortened - R. J. Mathar, Sep 16 2009

Status

approved