A202448 - OEIS

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A202448

Least k such that k*n!! +1 is a prime number.

1

1, 1, 2, 2, 2, 2, 2, 2, 8, 2, 10, 3, 2, 6, 10, 3, 2, 2, 14, 5, 10, 9, 6, 2, 22, 10, 4, 2, 26, 2, 22, 3, 8, 11, 30, 11, 6, 4, 2, 15, 52, 10, 22, 13, 10, 9, 34, 11, 18, 18, 2, 10, 26, 12, 4, 34, 4, 18, 26, 16, 34, 25, 22, 12, 14, 32, 50, 24, 4, 8, 12, 14, 26, 4

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..74.

EXAMPLE

a(9) = 8 because 8*9!! + 1 = 8*945 + 1 = 7561 is prime.

MATHEMATICA

Table[k = 0; While[!PrimeQ[k*n!! +1], k++]; k, {n, 85}]

CROSSREFS

Sequence in context: A139813 A172009 A299150 * A339165 A129381 A319991

Adjacent sequences: A202445 A202446 A202447 * A202449 A202450 A202451

KEYWORD

nonn

AUTHOR

Michel Lagneau, Dec 19 2011

STATUS

approved