A283559 Numbers k such that k![10]-2 is prime, where k![10] is the ten-fold multifactorial.

4, 5, 7, 9, 13, 15, 21, 25, 29, 31, 33, 41, 45, 49, 77, 195, 197, 199, 211, 309, 319, 345, 349, 395, 509, 533, 539, 597, 615, 705, 781, 803, 869, 969, 1313, 1317, 1331, 1335, 1337, 1429, 1597, 2121, 2133, 2513, 2547, 2733, 2885, 2931, 3701, 3709, 4681, 5911, 5933, 6125, 8191, 10637, 10679, 10845, 14901, 15629, 17165, 21691, 21867, 23119, 27033, 28601, 31245, 31957, 33289, 35773, 45011, 51079, 63241, 81369, 92615

Offset

1,1

Comments

a(76) > 50000.

The first 13 primes associated with this sequence: 2, 3, 5, 7, 37, 73, 229, 1873, 4957, 7159, 29599, 293599, 2953123.

Links

Table of n, a(n) for n=1..75.

C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75

Ken Davis, Status of Search for Multifactorial Primes.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[2, 50000], PrimeQ[MultiFactorial[#, 10] - 2] &]

Crossrefs

Cf. A076185, A085158, A094144, A204657.

Sequence in context: A263427 A052147 A139690 * A284190 A035266 A035264

Adjacent sequences: A283556 A283557 A283558 * A283560 A283561 A283562

Keyword

nonn

Author

Robert Price, Mar 10 2017

Extensions

a(72)-a(75) from Robert Price, Apr 03 2017

Status

approved