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URL: https://oeis.org/A109019

⇱ A109019 - OEIS

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A109019
Numbers whose digit reversal is different and has the same number of prime factors (with multiplicity).
3
13, 15, 17, 26, 31, 37, 39, 49, 51, 58, 62, 71, 73, 79, 85, 93, 94, 97, 107, 113, 115, 117, 122, 123, 126, 129, 143, 147, 149, 155, 157, 158, 159, 165, 167, 169, 177, 178, 179, 183, 185, 187, 199, 203, 205, 221, 225, 226, 244, 246, 265, 270, 285, 286, 289, 290
OFFSET
1,1
COMMENTS
Ray Chandler has coauthorship credit for this sequence.
LINKS
Eric Weisstein's World of Mathematics, Almost Prime.
Eric Weisstein's World of Mathematics, Emirp.
Eric Weisstein's World of Mathematics, Emirpimes.
FORMULA
{A006567} U {A097393} U {A109023} U {A109024} U ... U {A109031} U ...
MATHEMATICA
Select[Range@1000, ! PalindromeQ@# && Differences@PrimeOmega@{#, IntegerReverse@#} == {0} &] (* Hans Rudolf Widmer, Jun 03 2022 *)
PROG
(Python)
from sympy import factorint
def Omega(n): return sum(factorint(n).values())
def ok(n): return n != (r:=int(str(n)[::-1])) and Omega(n) == Omega(r)
print([k for k in range(300) if ok(k)]) # Michael S. Branicky, Mar 05 2026
KEYWORD
nonn,base
AUTHOR
Jonathan Vos Post, Jun 16 2005
EXTENSIONS
More terms from Stefan Steinerberger, Jun 16 2007
STATUS
approved