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A233745 a(n) = smallest number > a(n-1) such that a(1)*a(2)*...*a(n) - 1 is nonprime. 1
1, 2, 5, 7, 8, 10, 11, 13, 14, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The numbers 3, 4, 6, 8, 9, 12, 15, 19, 30, 31, 81, 152, 390, ... are not in the sequence.

LINKS

Table of n, a(n) for n=1..67.

EXAMPLE

1-1 = 0, 1*2-1 = 1, 1*2*5-1 = 9, 1*2*5*7 - 1 = 69, etc. are nonprimes.

MATHEMATICA

seq={1}; Do[n=Last[seq]+1; While[PrimeQ[n Times@@seq-1], n++]; AppendTo[ seq, n]; , {60}]; seq

CROSSREFS

Cf. A051957, A233746.

Sequence in context: A191767 A050086 A285352 * A283778 A028782 A025505

Adjacent sequences:  A233742 A233743 A233744 * A233746 A233747 A233748

KEYWORD

nonn

AUTHOR

Michel Lagneau, Dec 15 2013

STATUS

approved

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Last modified February 18 20:01 EST 2019. Contains 320262 sequences. (Running on oeis4.)