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A067268
Numbers k such that k and k^2+1 have the same number of distinct prime factors.
1
2, 4, 12, 15, 16, 18, 22, 28, 34, 35, 38, 39, 44, 45, 46, 48, 50, 51, 52, 58, 62, 65, 68, 69, 76, 80, 82, 85, 86, 88, 92, 95, 96, 100, 104, 105, 106, 108, 118, 132, 136, 138, 141, 144, 145, 152, 158, 159, 164, 166, 171, 174, 175, 178, 188, 194, 196, 201, 202, 205
OFFSET
1,1
LINKS
FORMULA
Numbers k such that omega(k) = omega(k^2+1).
EXAMPLE
2 is a term since omega(2) = omega(2^2+1) = 1.
MATHEMATICA
Select[Range[250], PrimeNu[#]==PrimeNu[#^2+1]&] (* Harvey P. Dale, Feb 07 2019 *)
PROG
(Magma) [k:k in [1.. 210 ]| #PrimeDivisors(k) eq #PrimeDivisors(k^2+1)]; // Marius A. Burtea, Feb 18 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 21 2002
STATUS
approved