1,1

primes indexed by 3-almostprimes = A124268. 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.

a(n) = 3almostprime(prime(n)) = A014612(A000040(n)).

a(1) = 3almostprime(prime(1)) = 3almostprime(2) = 12 = 2^2 * 3.

a(2) = 3almostprime(prime(2)) = 3almostprime(3) = 18 = 2 * 3^2.

a(3) = 3almostprime(prime(3)) = 3almostprime(5) = 27 = 3^3.

Cf. A000040, A014612, A122824, A124268, A124270.

Sequence in context: A076485 A071354 A006622 this_sequence A112054 A138636 A075281

Adjacent sequences: A124266 A124267 A124268 this_sequence A124270 A124271 A124272

easy,nonn

Jonathan Vos Post (jvospost3(AT)gmail.com), Oct 23 2006