A366809 The sum of the divisors of prime(n)#-1 where p# is the product of all the primes from 2 to p inclusive.

1, 6, 30, 240, 2310, 30030, 518940, 9943560, 230876448, 6551588160, 200561595684, 7471933410000, 304250263527210, 13082853940673340, 618109122639794688, 32589631537463089128, 1922760350251477679196, 117386696543681561301312, 7906535060701218163040640

Offset

1,2

Links

Table of n, a(n) for n=1..19.

Formula

a(n) = sigma(prime(n)#-1) = A000230(A057588(n)).

Example

a(4)=240 because the divisors of 7#-1 = 209 are {1, 11, 19, 209}.

Maple

seq(numtheory[sigma](mul(ithprime(k), k=1..n)-1), n=1..30);

Mathematica

DivisorSigma[1, #]&/@(FoldList[Times, Prime[Range[20]]]-1) (* Harvey P. Dale, Oct 20 2025 *)

Crossrefs

Cf. A057588, A000230, A054989, A366809, A064145.

Sequence in context: A126751 A009689 A228873 * A133668 A121772 A270845

Adjacent sequences: A366806 A366807 A366808 * A366810 A366811 A366812

Keyword

nonn

Author

Sean A. Irvine, Oct 23 2023

Status

approved