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A172125 a(n) = smallest prime of the form n*(n+1)*(n+2)...(n+k-1) - 1, or zero if no such a prime exists. 1
5, 5, 2, 3, 29, 5, 503, 7, 89, 109, 131, 11, 181, 13, 239, 271, 5813, 17, 379, 19, 461, 12143, 13799, 23, 53916693990528892723199999, 701, 657719, 811, 968330879, 29, 991, 31, 5339572260422399, 42839, 1259, 257256702743039, 54833, 37, 1559, 68879 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A conjecture is that no term is zero.

LINKS

Table of n, a(n) for n=1..40.

EXAMPLE

a(1)=5 because 1-1=0 and 1*2-1=1 are not primes, but 1*2*3-1=5 is.

MATHEMATICA

a[n_] := Block[{}, For[s = n; k = 1, ! PrimeQ[s - 1], s *= n + k; k++ ]; s - 1]; Table[a[n], {n, 1, 100}]

CROSSREFS

Cf. A172130, A087564, A172133

Sequence in context: A319905 A319593 A335321 * A125642 A247039 A011335

Adjacent sequences:  A172122 A172123 A172124 * A172126 A172127 A172128

KEYWORD

nonn

AUTHOR

Cheng Zhang (cz1(AT)rice.edu), Jan 26 2010, Mar 02 2010

STATUS

approved

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Last modified August 4 12:33 EDT 2021. Contains 346447 sequences. (Running on oeis4.)