A118333 Largest prime factor of n!! + (n+1)!!.

2, 3, 5, 11, 23, 7, 17, 163, 443, 29, 73, 251, 4027, 2477, 499, 199, 883, 47, 2671, 308333, 2099, 859, 510481, 10429, 514519, 29629, 51713, 42337, 5407, 13841, 151733, 2448023843, 3133033, 89101, 61613, 19448653009, 50136277, 63259211

Offset

0,1

Comments

First five terms coincide with A118332 because n!! + (n+1)!! is prime for n = 0, 1, 2, 3, 4. At n>4, n!! + (n+1)!! is always composite.

Links

Harvey P. Dale, Table of n, a(n) for n = 0..100

Mathematica

Table[FactorInteger[n!!+(n+1)!! ][[ -1, 1]], {n, 0, 40}]
FactorInteger[#][[-1, 1]]&/@(Total/@Partition[Range[0, 40]!!, 2, 1]) (* Harvey P. Dale, Mar 22 2019 *)

Crossrefs

Cf. A118332.

Sequence in context: A073879 A073880 A118332 * A131101 A188534 A214196

Adjacent sequences: A118330 A118331 A118332 * A118334 A118335 A118336

Keyword

nonn

Author

Zak Seidov, Apr 23 2006

Status

approved