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A162422 Numbers with at least 2 different numbers of digits among their prime factors. 1
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 (list; graph; refs; listen; history; text; internal format)
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
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
Sequence in context: A160078 A066059 A084891 * A063940 A046442 A101549
KEYWORD
base,nonn
AUTHOR
Cino Hilliard, Jul 03 2009
EXTENSIONS
Offset set to 1, definition shortened - R. J. Mathar, Sep 16 2009
STATUS
approved

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Last modified July 19 16:24 EDT 2024. Contains 374410 sequences. (Running on oeis4.)