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A074165 Numbers n such that n!!! is an interprime. 1
4, 6, 13, 15, 16, 23, 28, 46, 126, 148, 285 (list; graph; refs; listen; history; text; internal format)
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: A225939 A191199 A247787 * A137821 A010061 A280557

Adjacent sequences:  A074162 A074163 A074164 * A074166 A074167 A074168

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Sep 16 2002

STATUS

approved

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Last modified March 25 10:31 EDT 2019. Contains 321470 sequences. (Running on oeis4.)