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A124282 Primes indexed by 4-almost primes. 8
53, 89, 151, 173, 251, 263, 281, 419, 433, 457, 463, 541, 569, 701, 743, 761, 769, 809, 863, 881, 911, 1097, 1129, 1193, 1213, 1249, 1291, 1373, 1427, 1439, 1459, 1481, 1571, 1583, 1657, 1783, 1931, 1949, 1951, 2017, 2029, 2087, 2203, 2213, 2287, 2297 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

4-almost primes indexed by primes = A124283. prime(4almostprime(n)) - 4almostprime(prime(n)) = A124284. Primes indexed by 3-almost primes = A124268. 3-almost primes indexed by primes = A124269. prime(3almostprime(n)) - 3almostprime(prime(n)) = A124270. See also A106349 Primes indexed by semiprimes. See also A106350 Semiprimes indexed by primes. See also A122824 Prime(semiprime(n)) - semiprime(prime(n)). Commutator [A000040,A001358] at n.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = prime(4almostprime(n)) = A000040(A014613(n)). {p such that p is prime and omega(primepi(p)) = 4} = {p such that p is in A000040 and A001222(A000720(p)) = 4}.

EXAMPLE

a(1) = prime(4almostprime(1)) = prime(16) = 53.

a(2) = prime(4almostprime(2)) = prime(24) = 89.

a(3) = prime(4almostprime(3)) = prime(36) = 151.

CROSSREFS

Cf. A000040, A014613, A114414, A122824, A124269, A124270, A124283, A124284.

Sequence in context: A214230 A272367 A119289 * A137869 A096697 A033234

Adjacent sequences:  A124279 A124280 A124281 * A124283 A124284 A124285

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Oct 24 2006

STATUS

approved

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Last modified December 9 13:50 EST 2019. Contains 329877 sequences. (Running on oeis4.)