A329063 a(n) = a(n-1)! + a(n-1) with a(1)=1.

1, 2, 4, 28, 304888344611713860501504000028

Offset

1,2

Comments

The next term is too large to include, since it has about 8.85695956*10^30 digits.

No term can be represented by a sum of three positive squares, because a(4) and the following terms can all be written as 4*(8*k+7) for k>=0.

Links

Table of n, a(n) for n=1..5.

Formula

a(n) = a(n-1)! + a(n-1)

Example

a(3) = a(3-1)! + a(3-1) = a(2)! + a(2) = 4.

Mathematica

a[1]=1; a[n_] := a[n-1]! + a[n-1]; Array[a, 5] (* Giovanni Resta, Nov 03 2019 *)

Crossrefs

Cf. A000408 (sums of 3 squares).

Sequence in context: A248872 A329102 A126580 * A124687 A267122 A018291

Adjacent sequences: A329060 A329061 A329062 * A329064 A329065 A329066

Keyword

nonn

Author

_Ananthakrishna Kaithalayil_, Nov 02 2019

Extensions

Edited by N. J. A. Sloane, Nov 03 2019

Status

approved