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A139421 a(1)=1; for n>1, a(n) = largest prime divisor of n!!. 8
1, 2, 3, 2, 5, 3, 7, 3, 7, 5, 11, 5, 13, 7, 13, 7, 17, 7, 19, 7, 19, 11, 23, 11, 23, 13, 23, 13, 29, 13, 31, 13, 31, 17, 31, 17, 37, 19, 37, 19, 41, 19, 43, 19, 43, 23, 47, 23, 47, 23, 47, 23, 53, 23, 53, 23, 53, 29, 59, 29, 61, 31, 61, 31, 61, 31, 67, 31, 67, 31, 71, 31, 73, 37 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A006530(A006882(n)). - Michel Marcus, Nov 08 2013

MATHEMATICA

a = {}; Do[b = First[Last[FactorInteger[n!! ]]]; AppendTo[a, b], {n, 2, 100}]; a

FactorInteger[#][[-1, 1]]&/@(Range[80]!!) (* Harvey P. Dale, Feb 15 2014 *)

CROSSREFS

Cf. A010693.

Sequence in context: A284695 A081812 A331634 * A219964 A165500 A072505

Adjacent sequences:  A139418 A139419 A139420 * A139422 A139423 A139424

KEYWORD

nonn

AUTHOR

Artur Jasinski, Apr 21 2008

STATUS

approved

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Last modified July 11 15:50 EDT 2020. Contains 335626 sequences. (Running on oeis4.)