A178607 Largest prime < n!! (double factorial of n).
2, 7, 13, 47, 103, 383, 941, 3833, 10391, 46073, 135131, 645097, 2027023, 10321919, 34459423, 185794463, 654729073, 3715891181, 13749310511, 81749606383, 316234143163, 1961990553581, 7905853580621, 51011754393599
Offset: 3
Keywords
Links
- Vincenzo Librandi, Table of n, a(n) for n = 3..200
Programs
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Mathematica
PrimePrev[n_]:=Module[{k},k=n-1;While[ !PrimeQ[k],k-- ];k]; Table[PrimePrev[n!! ],{n,3,40}] NextPrime[#,-1]&/@(Range[3,30]!!) (* Harvey P. Dale, Jul 13 2015 *) -
PARI
a(n)=if(n<2, 1, n*a(n-2)); for(n=3,26,print1(precprime(a(n)-1)", ")); \\ Graziano Aglietti (mg5055(AT)mclink.it), Aug 23 2010
Formula
Extensions
Offset corrected by R. J. Mathar, Jun 23 2010