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A229125 Numbers of the form p * m^2, where p is prime and m > 0: union of A228056 and A000040. 11
2, 3, 5, 7, 8, 11, 12, 13, 17, 18, 19, 20, 23, 27, 28, 29, 31, 32, 37, 41, 43, 44, 45, 47, 48, 50, 52, 53, 59, 61, 63, 67, 68, 71, 72, 73, 75, 76, 79, 80, 83, 89, 92, 97, 98, 99, 101, 103, 107, 108, 109, 112, 113, 116, 117, 124, 125, 127, 128, 131, 137, 139, 147, 148, 149 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
No term is the product of two other terms.
Squares of terms and pairwise products of distinct terms form a subsequence of A028260.
Numbers n such that A162642(n) = 1. - Jason Kimberley, Oct 10 2016
Numbers k such that A007913(k) is a prime number. - Amiram Eldar, Jul 27 2020
LINKS
FORMULA
The number of terms not exceeding x is (Pi^2/6) * x/log(x) + O(x/(log(x))^2) (Cohen, 1962). - Amiram Eldar, Jul 27 2020
MATHEMATICA
With[{nn=70}, Take[Union[Flatten[Table[p*m^2, {p, Prime[Range[nn]]}, {m, nn}]]], nn]] (* Harvey P. Dale, Dec 02 2014 *)
PROG
(PARI) test(n)=isprime(core(n))
for(n=1, 200, if(test(n), print1(n", ")))
CROSSREFS
Subsequence of A026424.
Sequence in context: A026424 A298207 A347453 * A228853 A141832 A066680
KEYWORD
nonn
AUTHOR
Chris Boyd, Sep 14 2013
STATUS
approved

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Last modified March 19 01:34 EDT 2024. Contains 370952 sequences. (Running on oeis4.)