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A124308 Primes indexed by 5-almost primes. 4
131, 223, 359, 409, 593, 613, 659, 953, 997, 1049, 1069, 1223, 1283, 1543, 1601, 1693, 1733, 1747, 1811, 1987, 2003, 2069, 2503, 2593, 2693, 2713, 2789, 2801, 2903, 3079, 3181, 3221, 3301, 3323, 3541, 3571, 3727, 4003, 4127, 4283 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..40.

FORMULA

a(n) = prime(5almostprime(n)) = A000040(A014614(n)). {p such that p is prime and omega(primepi(p)) = 5} = {p such that p is in A000040 and A001222(A000720(p)) = 5}.

EXAMPLE

a(1) = prime(5almostprime(1)) = prime(32 = 2^5) = 131.

a(2) = prime(5almostprime(2)) = prime(48 = 2^4 * 3) = 223.

a(3) = prime(5almostprime(3)) = prime(72 = 2^3 * 3^2) = 359.

a(4) = prime(5almostprime(4)) = prime(80 = 2^4 * 5) = 409.

MATHEMATICA

Prime[#]&/@Select[Range[600], PrimeOmega[#]==5&] (* Harvey P. Dale, Nov 20 2015 *)

CROSSREFS

Cf. A124309 5-almost primes indexed by primes. A124310 prime(5almostprime(n)) - 5almostprime(prime(n)). 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.

Cf. A000040, A014614, A114405, A114415, A122824, A124269, A124270, A124282-A124284, A124309, A124310.

Sequence in context: A088288 A142068 A141920 * A059702 A142442 A288410

Adjacent sequences:  A124305 A124306 A124307 * A124309 A124310 A124311

KEYWORD

easy,nonn,less

AUTHOR

Jonathan Vos Post, Oct 25 2006

STATUS

approved

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Last modified October 16 09:02 EDT 2021. Contains 348041 sequences. (Running on oeis4.)