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

8, 36, 120, 252, 550, 936, 1666, 2280, 3312, 5220, 6820, 9324, 11726, 14448, 17625, 22048, 27081, 30744, 38190, 45440, 50589, 59092, 66815, 76896, 92150, 102414, 111240, 125832, 139084, 152550, 181102, 201216, 221529, 236300, 265965, 282672, 313686, 340670, 364728, 394440

Offset

1,1

Links

Andrew Howroyd, Table of n, a(n) for n = 1..10000

Formula

a(n) = n*prime(n)*composite(n).

a(n) = n*A067563(n).

Example

For n=1; prime(1)=2, composite(1)=4; a(1) = 8;
For n=2; prime(2)=3, composite(2)=6; a(2) = 36;
For n=3; prime(3)=5, composite(3)=8; a(3) = 120.

Mathematica

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 *)
Module[{nn=100, c, len, p}, c=Select[Range[nn], CompositeQ]; len=Length[c]; p=Prime[Range[len]]; Table[n c[[n]]p[[n]], {n, len}]] (* Harvey P. Dale, Nov 28 2025 *)

Crossrefs

Cf. A000040, A002808, A067563.

Sequence in context: A014343 A381794 A162596 * A341137 A051192 A008500

Adjacent sequences: A331996 A331997 A331998 * A332000 A332001 A332002

Keyword

nonn

Author

Soham B. Patel, Feb 04 2020

Status

approved