A217723 a(n) = (sum of first n primorial numbers) minus 1.

1, 7, 37, 247, 2557, 32587, 543097, 10242787, 233335657, 6703028887, 207263519017, 7628001653827, 311878265181037, 13394639596851067, 628284422185342477, 33217442899375387207, 1955977793053588026277, 119244359152460559009547

Offset

1,2

Links

Paul Larm (terms 1..20) and Amiram Eldar (terms 21..100), Table of n, a(n) for n = 1..100

Paul Larm, Table of a(n) for n = 2..25 showing prime factors.

Formula

a(1) = P(1)# - 1, a(2) = P(1)# + P(2)# -1; where P(n)# is the product of first n prime numbers (primorial#).

Example

For n = 4, a(4) = 2 + 2*3 + 2*3*5 + 2*3*5*7 - 1 = 247.

Mathematica

Accumulate[Denominator[Accumulate[1/Prime[Range[20]]]]] - 1 (* Alonso del Arte, Mar 21 2013 *)
Accumulate[Table[Fold[Times, Prime[Range[n]]], {n, 20}]]-1 (* Harvey P. Dale, May 23 2020 *)

Crossrefs

Equals A060389 - 1. Cf. A223546, A223548.

Sequence in context: A361279 A096965 A159597 * A100309 A198410 A199192

Adjacent sequences: A217720 A217721 A217722 * A217724 A217725 A217726

Keyword

nonn,easy

Author

Paul Larm, Mar 21 2013

Status

approved