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 A119323 Least prime p such that n*p#-1 is prime. 2
 3, 2, 2, 2, 3, 2, 2, 3, 2, 2, 7, 2, 5, 3, 2, 2, 3, 3, 2, 5, 2, 2, 3, 2, 3, 29, 2, 3, 3, 2, 2, 3, 3, 2, 5, 2, 2, 3, 3, 2, 5, 2, 3, 3, 2, 17, 3, 5, 2, 5, 2, 2, 3, 2, 2, 13, 2, 3, 3, 3, 7, 13, 5, 2, 3, 2, 3, 5, 2, 2, 5, 3, 7, 3, 2, 2, 3, 3, 2, 3, 13, 2, 19, 2, 3, 5, 2, 11, 11, 2, 2, 7, 3, 3, 3, 2, 2, 3, 2, 2, 19, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 1*(2*3)-1=5 prime so a(1)= 3 as 3# = 2*3. 2*(2)-1=3 prime so a(2)= 2 as 2# = 2. PROG (PARI) a(n) = {my(k = 1); while (!isprime(n*prod(j=1, k, prime(j)) - 1), k++); prime(k); } \\ Michel Marcus, Sep 14 2019 CROSSREFS Cf. A002110 (primorials), A119324. Sequence in context: A127599 A207384 A085034 * A102299 A302481 A306542 Adjacent sequences:  A119320 A119321 A119322 * A119324 A119325 A119326 KEYWORD easy,nonn AUTHOR Pierre CAMI, May 14 2006 EXTENSIONS More terms from David Wasserman, Jun 20 2007 STATUS approved

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Last modified December 12 22:06 EST 2019. Contains 329963 sequences. (Running on oeis4.)