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 A135396 a(n) = Product_{d|n} (n-d)!. 2
 1, 1, 2, 12, 24, 17280, 720, 87091200, 29030400, 1755758592000, 3628800, 1525930675524002119680000000, 479001600, 15033074749223731200000, 151533393472175210496000000, 2201737050440244933006930739200000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS G. C. Greubel, Table of n, a(n) for n = 1..100 FORMULA If p prime, a(p) = (p-1)!. - Bernard Schott, Nov 15 2021 EXAMPLE For n = 6, the divisors of 6 are 1,2,3,6; a(6) = (6-1)! * (6-2)! * (6-3)! * (6-6)! = 17280. MAPLE A135396 := proc(n) local dvs ; dvs := numtheory[divisors](n) minus {n} ; mul( (n-i)!, i=dvs) ; end: seq(A135396(n), n=1..30) ; # R. J. Mathar, Feb 19 2008 MATHEMATICA Table[Product[(n - Divisors[n][[i]])!, {i, 1, Length[Divisors[n]]}], {n, 1, 20}] (* Stefan Steinerberger, Feb 19 2008 *) Table[Times@@((n-Divisors[n])!), {n, 20}] (* Harvey P. Dale, Dec 10 2014 *) PROG (PARI) a(n)=my(s=1); fordiv(n, d, s*=(n-d)!); s \\ Charles R Greathouse IV, Oct 12 2016 CROSSREFS Cf. A000142. Cf. A000010 (comments on product formulas). Sequence in context: A091137 A347284 A092825 * A031048 A294554 A098707 Adjacent sequences:  A135393 A135394 A135395 * A135397 A135398 A135399 KEYWORD easy,nonn AUTHOR Ctibor O. Zizka, Feb 17 2008 EXTENSIONS Definition simplified by Stefan Steinerberger, Feb 19 2008 More terms from R. J. Mathar and Stefan Steinerberger, Feb 19 2008 STATUS approved

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Last modified August 14 10:58 EDT 2022. Contains 356116 sequences. (Running on oeis4.)