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A178607 Largest prime < n!! (double factorial of n). 1
2, 7, 13, 47, 103, 383, 941, 3833, 10391, 46073, 135131, 645097, 2027023, 10321919, 34459423, 185794463, 654729073, 3715891181, 13749310511, 81749606383, 316234143163, 1961990553581, 7905853580621, 51011754393599 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 3..200

FORMULA

a(n) = A151799(A006882(n)) [R. J. Mathar, Jun 23 2010]

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 *)

PROG

(PARI) a(n)=if(n<2, 1, n*a(n-2)); for(n=3, 26, print1(precprime(a(n)-1)", ")); [From Graziano Aglietti (mg5055(AT)mclink.it), Aug 23 2010]

CROSSREFS

Cf. A006882, A006990, A037151, A178606

Sequence in context: A262727 A129592 A153136 * A127487 A226140 A180003

Adjacent sequences:  A178604 A178605 A178606 * A178608 A178609 A178610

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, May 30 2010

EXTENSIONS

Offset corrected by R. J. Mathar, Jun 23 2010

STATUS

approved

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Last modified December 10 19:15 EST 2016. Contains 279005 sequences.