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A089229
Neither primes nor square numbers.
10
6, 8, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 40, 42, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 102, 104, 105, 106
OFFSET
1,1
COMMENTS
Also, composites with an even number of divisors. - Juri-Stepan Gerasimov, Jul 17 2009
FORMULA
(1 - A010051(a(n))) * (1 - A010052(a(n))) = 1. - Reinhard Zumkeller, Jul 07 2014
MATHEMATICA
m=100; Complement[Range[0, m^2], Range[0, m]^2, Prime[Range[PrimePi[m^2]]]] (* Zak Seidov, Dec 12 2011*)
PROG
(Haskell)
a089229 n = a089229_list !! (n-1)
a089229_list = f a018252_list $ tail a000290_list where
f (u:us) vs'@(v:vs) = if u < v then u : f us vs' else f us vs
-- Reinhard Zumkeller, Jul 07 2014
(PARI) lista(nn) = for (n=1, nn, if (!issquare(n) && !isprime(n), print1(n, ", "))); \\ Michel Marcus, Jun 01 2015
(PARI) is(n)=!issquare(n) && !isprime(n) \\ Charles R Greathouse IV, Oct 19 2015
(Magma) [n: n in [1..200] | not IsSquare(n) and not IsPrime(n)]; // Vincenzo Librandi, Jun 14 2016
(Python)
from math import isqrt
from sympy import primepi
def A089229(n):
def f(x): return int(n+primepi(x)+isqrt(x))
m, k = n, f(n)
while m != k: m, k = k, f(k)
return m # Chai Wah Wu, Oct 12 2024
CROSSREFS
Complement of A089237.
Sequence in context: A050199 A268388 A139118 * A345945 A123240 A131181
KEYWORD
nonn
AUTHOR
Roger L. Bagula, Dec 10 2003
STATUS
approved