A129516 Numbers k such that k divides (k-1)!! - 1.

1, 2, 8, 11, 16, 19, 23, 31, 32, 43, 64, 67, 71, 128, 131, 151, 163, 167, 179, 223, 227, 239, 256, 271, 311, 347, 359, 419, 439, 443, 463, 487, 491, 512, 523, 563, 571, 619, 647, 683, 691, 719, 739, 751, 787, 911, 919, 947, 967, 983, 1019, 1024, 1031, 1039

Offset

1,2

Comments

Terms include all powers of 2 except 2^2 and some primes of the form 4m+3 belonging to A002145. Odd primes in this sequence are listed in A129517. A002145 is the union of A129517 and A129518 (numbers m > 2 such that m divides (m-2)!!-1 and (m-3)!!-1).

Links

Table of n, a(n) for n=1..54.

Mathematica

Select[Range[2048], IntegerQ[((#-1)!!-1)/# ]&]

Crossrefs

Cf. A006882 (double factorials).

Cf. A002145 (primes of the form 4k+3).

Cf. A129517 (odd primes p such that p divides (p-1)!!-1).

Cf. A129518 (numbers k > 2 such that k divides (k-2)!!-1 and (k-3)!!-1).

Sequence in context: A366915 A379140 A064105 * A220269 A143189 A056550

Adjacent sequences: A129513 A129514 A129515 * A129517 A129518 A129519

Keyword

nonn

Author

Alexander Adamchuk, Apr 18 2007

Status

approved