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A065314
Smallest prime divisor of (n-th primorial - (n+1)-st prime).
6
23, 199, 2297, 30013, 41, 9699667, 2819, 53, 21701, 79, 163, 181, 61, 1619, 14669, 307, 103, 306091, 907, 3217644767340672907899084554047, 267064515689275851355624017992701, 23768741896345550770650537601358213
OFFSET
3,1
LINKS
Tyler Busby, Table of n, a(n) for n = 3..83 (terms 3..40 from Michel Marcus, terms 41..80 from Sean A. Irvine)
FORMULA
a(n) = A020639( A002110(n) - A000040(n+1) ).
EXAMPLE
For n=3, 3rd primorial=30, prime(4)=7, difference=23, so a(3)=23.
MATHEMATICA
Map[FactorInteger[Times @@ #1 - #2][[1, 1, 1]] & @@ Reverse@ TakeDrop[#, -1] &, Drop[#, 3] &@ FoldList[Flatten@ Append[{#1}, #2] &, Prime@ Range@ 25]] (* Michael De Vlieger, Jul 16 2017 *)
PROG
(PARI) a(n) = vecmin(factor(prod(k=1, n, prime(k)) - prime(n+1))[, 1]); \\ Michel Marcus, Jul 16 2017
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 29 2001
STATUS
approved