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A279098 Numbers k such that prime(k) divides primorial(j) + 1 for exactly one integer j. 5
1, 2, 4, 8, 11, 17, 18, 21, 25, 32, 34, 35, 39, 40, 42, 47, 48, 58, 63, 65, 66, 67, 69, 90, 91, 97, 105, 110, 122, 140, 144, 151, 152, 162, 166, 168, 173, 174, 175, 179, 180, 186, 205, 207, 208, 210, 211, 218, 233, 243, 249, 256, 261, 262, 297, 308, 316, 318 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

As used here, "primorial(j)" refers to the product of the first j primes, i.e., A002110(j).

Primorial(j) + 1 is the j-th Euclid number, A006862(j).

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..10000

EXAMPLE

59 is not in this sequence because both primorial(7) + 1 = 510511 and primorial(17) + 1 = 1922760350154212639071 are divisible by prime(59) = 277.

MATHEMATICA

np[1]=1; np[n_] := Block[{c=0, p=Prime[n], trg, x=1}, trg = p-1; Do[x = Mod[x Prime[k], p]; If[trg == x, c++], {k, n-1}]; c]; Select[Range[262], np[#] == 1 &] (* Giovanni Resta, Mar 29 2017 *)

CROSSREFS

Subsequence of A279097 (which also includes numbers k such that prime(k) divides primorial(j) + 1 for more than one integer j).

Cf. A000040, A002110, A006862, A113165, A279099, A283928.

Sequence in context: A018320 A153195 A279097 * A010068 A295674 A120632

Adjacent sequences:  A279095 A279096 A279097 * A279099 A279100 A279101

KEYWORD

nonn

AUTHOR

Jon E. Schoenfield, Mar 24 2017

STATUS

approved

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Last modified September 30 11:32 EDT 2020. Contains 337439 sequences. (Running on oeis4.)