A110376 - OEIS

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A110376

a(n) = Sum_{r < n, gcd(r,n)=1} n!/r.

1, 2, 9, 32, 250, 864, 12348, 67584, 804816, 5760000, 116915040, 686776320, 19323757440, 157991178240, 2951575200000, 42301705420800, 1202482800691200, 10048607738265600, 425162773111910400, 4541227794432000000

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

a(6) = 6!(1/1 + 1/5) = 864.

MAPLE

a:=proc(n) local s, r: s:=0: for r from 1 to n do if gcd(r, n)=1 then s:=s+1/r else s:=s: fi: od: n!*s end: seq(a(n), n=1..23); # Emeric Deutsch, Jul 25 2005

MATHEMATICA

Do[Print[n! * Plus @@ Map[(1/#)&, Select[Range[n], GCD[ #, n] == 1 &]]], {n, 1, 30}] (* Ryan Propper, Jul 25 2005 *)

CROSSREFS

Cf. A038048, A110373, A110374.

Sequence in context: A179230 A114853 A331727 * A335577 A338437 A296151

Adjacent sequences: A110373 A110374 A110375 * A110377 A110378 A110379

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Jul 24 2005

EXTENSIONS

More terms from Emeric Deutsch, Ryan Propper and Reinhard Zumkeller, Jul 25 2005

STATUS

approved