login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

2..a(n) is the smallest range in which the most common value of Omega(k) is n, where Omega(k) is the number of prime factors of k (A001222).
2

%I #4 May 21 2016 14:22:13

%S 2,26,15526,151165506068

%N 2..a(n) is the smallest range in which the most common value of Omega(k) is n, where Omega(k) is the number of prime factors of k (A001222).

%e Among the numbers from 2 to a(2)=26 the most common value of Omega is 2. Indeed, there are 9 numbers for which Omega is 1 (the primes) and 10 for which Omega is 2 (the semiprimes).

%t a[n_] := Block[{c1=0, c2=0, v, k=1}, While[c2<=c1, v=PrimeOmega[++k]; If[v == n-1, c1++]; If[v == n, c2++]]; k]; Array[a, 3]

%Y Cf. A001222, A273380.

%K nonn,more

%O 1,1

%A _Giovanni Resta_, May 21 2016