A074165 Numbers n such that n!!! is an interprime.

4, 6, 13, 15, 16, 23, 28, 46, 126, 148, 285

Offset

1,1

Comments

No additional terms up to n = 700. - Harvey P. Dale, Aug 02 2018

Links

Table of n, a(n) for n=1..11.

Mathematica

PrevPrim[n_] := Block[{k = n - 1}, While[ ! PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ ! PrimeQ[k], k++ ]; k]; NFactorialM[n_, m_] := Block[{k = n, p = n}, While[k > m, k -= m; p = p*k]; p]; Do[ a = NFactorialM[n, 3]; If[2a == PrevPrim[a] + NextPrim[a], Print[n]], {n, 3, 500}]
npipQ[n_]:=Module[{p=Times@@Range[n, 1, -3]}, p==Mean[{NextPrime[ p], NextPrime[ p, -1]}]]; Select[Range[300], npipQ] (* Harvey P. Dale, Aug 02 2018 *)

Crossrefs

Cf. A053709 & A074176.

Sequence in context: A191199 A354089 A247787 * A137821 A010061 A280557

Adjacent sequences: A074162 A074163 A074164 * A074166 A074167 A074168

Keyword

nonn

Author

Robert G. Wilson v, Sep 16 2002

Status

approved