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A217723 a(n) = (sum of first n primorial numbers) minus 1. 3
1, 7, 37, 247, 2557, 32587, 543097, 10242787, 233335657, 6703028887, 207263519017, 7628001653827, 311878265181037, 13394639596851067, 628284422185342477, 33217442899375387207, 1955977793053588026277, 119244359152460559009547 (list; graph; refs; listen; history; text; internal format)
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 *)

CROSSREFS

Equals A060389 - 1. Cf. A223546, A223548.

Sequence in context: A102760 A096965 A159597 * A100309 A198410 A199192

Adjacent sequences:  A217720 A217721 A217722 * A217724 A217725 A217726

KEYWORD

nonn,easy

AUTHOR

Paul Larm, Mar 21 2013

STATUS

approved

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Last modified December 12 09:36 EST 2019. Contains 329953 sequences. (Running on oeis4.)