cp's OEIS Frontend

A331999 a(n) is the product of n, the n-th prime and the n-th composite number.

%I A331999 #21 Apr 11 2020 11:45:43
%S A331999 8,36,120,252,550,936,1666,2280,3312,5220,6820,9324,11726,14448,17625,
%T A331999 22048,27081,30744,38190,45440,50589,59092,66815,76896,92150,102414,
%U A331999 111240
%N A331999 a(n) is the product of n, the n-th prime and the n-th composite number.
%F A331999 a(n) = n*prime(n)*composite(n).
%F A331999 a(n) = n*A067563(n).
%e A331999 For n=1; prime(1)=2, composite(1)=4; a(1) = 8;
%e A331999 For n=2; prime(2)=3, composite(2)=6; a(2) = 36;
%e A331999 For n=3; prime(3)=5, composite(3)=8; a(3) = 120.
%t A331999 m = 105; p = Select[Range[m], PrimeQ]; n = Length[p]; c = Complement[Range[2, m], p][[1;;n]]; p * c * Range[n] (* _Amiram Eldar_, Feb 12 2020 *)
%Y A331999 Cf. A000040, A002808, A067563.
%K A331999 nonn
%O A331999 1,1
%A A331999 _Soham B. Patel_, Feb 04 2020