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A050699 Nonprime numbers n such that n and n-reversed (<> n and no leading zeros) have the same number of prime factors (counted with multiplicity). 4
15, 26, 39, 49, 51, 58, 62, 85, 93, 94, 115, 117, 122, 123, 126, 129, 143, 147, 155, 158, 159, 165, 169, 177, 178, 183, 185, 187, 203, 205, 221, 225, 226, 244, 246, 265, 285, 286, 289, 294, 302, 314, 315, 319, 321, 326, 327, 329, 335, 338, 339, 341, 355, 366 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
E.g., 321 = 3*107 and 123 = 3*41 -> both 321 and 123 have two prime factors.
MAPLE
with(numtheory): read(transforms): for n from 12 to 366 do r:=digrev(n): if(not isprime(n) and not n=r and not n mod 10 = 0 and bigomega(n)=bigomega(r))then printf("%d, ", n); fi: od: # Nathaniel Johnston, Jun 23 2011
MATHEMATICA
nrnQ[n_]:=Module[{idn=IntegerDigits[n], rev}, rev=Reverse[idn]; !PrimeQ[n] &&First[rev]!=0&&idn!=rev&&PrimeOmega[n]==PrimeOmega[FromDigits[rev]]]; Select[Range[400], nrnQ] (* Harvey P. Dale, Jun 23 2011 *)
CROSSREFS
Sequence in context: A189045 A366961 A032609 * A097393 A050700 A263108
KEYWORD
nonn,base,easy
AUTHOR
Patrick De Geest, Aug 15 1999
EXTENSIONS
Definition clarified by Harvey P. Dale, Jun 23 2011
STATUS
approved

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Last modified March 19 04:26 EDT 2024. Contains 370952 sequences. (Running on oeis4.)