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A175193 a(n) is the smallest positive integer such that (the n-th prime)+a(n)! is prime, or -1 if no such prime exists. 4
1, 2, 2, 3, 2, 3, 2, 4, 3, 2, 3, 3, 2, 4, 3, 3, 2, 3, 3, 2, 3, 4, 3, 4, 3, 2, 3, 2, 5, 4, 4, 3, 2, 4, 2, 3, 3, 5, 3, 3, 2, 9, 2, 3, 2, 4, 5, 3, 2, 5, 3, 2, 7, 3, 3, 3, 2, 3, 3, 2, 4, 4, 3, 2, 4, 8, 3, 5, 2, 4, 3, 4, 3, 3, 5, 3, 5, 4, 5, 4, 2, 5, 2, 3, 4, 3, 5, 3, 2, 4, 4, 4, 5, 7, 4, 3, 6, 2, 4, 3, 4, 3, 3, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A175194(n) = a(n)!.

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Michael De Vlieger, First positions of values and records in a(n).

FORMULA

A092789(n) = A000040(n) + a(n)!.

EXAMPLE

From Michael De Vlieger, Nov 24 2017: (Start)

Records and their indices in a(n):

    i          n   a(n)

   --------------------

    1        1      1

    2        2      2

    3        4      3

    4        8      4

    5       29      5

    6       42      9

    7      233     10

    8      254     42

    9     4508     49

   10     7003    124

   11     7385    276

   12    60650    311

   13    97146    542

(End)

MATHEMATICA

Fold[Append[#1, SelectFirst[Range[12], Function[k, PrimeQ[Prime[#2] + k!]]]] &, {1}, Range[2, 105]] (* Michael De Vlieger, Nov 24 2017 *)

PROG

(PARI) a(n) = {my(k = 1, p = prime(n)); while (!isprime(p + k!), k++); k; } \\ Michel Marcus, Nov 25 2017

CROSSREFS

Cf. A082470, A092789, A175194.

Sequence in context: A065151 A320013 A299990 * A073093 A222084 A088873

Adjacent sequences:  A175190 A175191 A175192 * A175194 A175195 A175196

KEYWORD

nonn

AUTHOR

Leroy Quet, Mar 01 2010

EXTENSIONS

Extended by Ray Chandler, Mar 04 2010

STATUS

approved

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Last modified November 20 15:12 EST 2018. Contains 317402 sequences. (Running on oeis4.)