A321581 a(n) is the sum of first n natural numbers raised to the product of first n natural numbers.

0, 1, 9, 46656, 1000000000000000000000000

Offset

0,3

Comments

The next term a(5) has 142 decimal digits.

Links

Table of n, a(n) for n=0..4.

Formula

a(n) = (n*(n+1)/2)^(n!).

a(n) = A000217(n)^A000142(n).

Example

a(3) = (1+2+3)^3! = 6^6 = 46656.

Maple

[(n*(n+1)/2)^factorial(n)$n=0..5]; # Muniru A Asiru, Dec 20 2018

Mathematica

a[n_] := (n*(n + 1)/2)^n!; Array[a, 5] (* Amiram Eldar, Nov 13 2018 *)

Prog

(PARI) a(n)=(n*(n+1)/2)^(n!); \\ Andrew Howroyd, Nov 13 2018
(GAP) List([1..5], n->(n*(n+1)/2)^(Factorial(n))); # Stefano Spezia, Nov 21 2018

Crossrefs

Cf. A000142, A000217, A067055.

Sequence in context: A242853 A198478 A159398 * A053971 A013790 A271103

Adjacent sequences: A321578 A321579 A321580 * A321582 A321583 A321584

Keyword

nonn,easy

Author

Ayush Kumar Jha, Nov 13 2018

Status

approved