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A336615
Numbers of the form p * m^2, where p is prime and m > 0 is not divisible by p.
2
2, 3, 5, 7, 11, 12, 13, 17, 18, 19, 20, 23, 28, 29, 31, 37, 41, 43, 44, 45, 47, 48, 50, 52, 53, 59, 61, 63, 67, 68, 71, 73, 75, 76, 79, 80, 83, 89, 92, 97, 98, 99, 101, 103, 107, 109, 112, 113, 116, 117, 124, 127, 131, 137, 139, 147, 148, 149, 151, 153, 157, 162
OFFSET
1,1
COMMENTS
Numbers k such that A008833(k) is a unitary divisor of k and A007913(k) = k / A008833(k) is a prime number.
FORMULA
The number of terms not exceeding x is (Pi^2/6) * x/log(x) + O(x/(log(x))^2) (Cohen, 1962).
MATHEMATICA
Select[Range[2, 200], Select[FactorInteger[#][[;; , 2]], OddQ] == {1} &]
CROSSREFS
Intersection of A229125 and A335275.
Subsequences: A000040, A054753, A179643.
Sequence in context: A336418 A212166 A293511 * A325337 A342119 A372742
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jul 27 2020
STATUS
approved