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A066838 Product of primes < n that do not divide n. 2
1, 1, 2, 3, 6, 5, 30, 105, 70, 21, 210, 385, 2310, 2145, 2002, 15015, 30030, 85085, 510510, 969969, 461890, 440895, 9699690, 37182145, 44618574, 8580495, 74364290, 15935205, 223092870, 215656441, 6469693230, 100280245065 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Robert Israel, Table of n, a(n) for n = 1..2350

FORMULA

a(prime(n)) = A002110(n-1). - Michel Marcus, May 20 2014

a(n) = e^[Sum_{k=2..n} (1-floor(n/k)+floor((n-1)/k))*A010051(k)*M(k)] where M(n) is the Mangoldt function. - Anthony Browne, Jun 17 2016

EXAMPLE

a(8) = 105 = 3 * 5 * 7 because 3, 5 and 7 are the primes < 8 that do not divide 8.

MAPLE

Primes:= select(isprime, [$2..100]):

seq(convert(select(t -> t <= n and n mod t <> 0, Primes), `*`), n=1..100); # Robert Israel, Jun 19 2016

MATHEMATICA

Table[Apply[Times, Select[Prime@ Range@ PrimePi@ n, CoprimeQ[#, n] &] /. {} -> 1], {n, 32}] (* or *)

Table[E^Sum[(1 - Floor[n/k] + Floor[(n - 1)/k]) Boole@ PrimeQ[k] MangoldtLambda@ k, {k, 2, n}], {n, 32}] (* Michael De Vlieger, Jun 22 2016 *)

PROG

(PARI) a(n) = prod(i=1, n-1, if (isprime(i) && (n%i) , i, 1)); \\ Michel Marcus, May 20 2014

CROSSREFS

Cf. A002110 (primorial numbers).

Sequence in context: A260443 A206242 A124655 * A228151 A276087 A084678

Adjacent sequences:  A066835 A066836 A066837 * A066839 A066840 A066841

KEYWORD

nonn

AUTHOR

Leroy Quet, Jan 20 2002

STATUS

approved

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Last modified July 18 15:41 EDT 2019. Contains 325144 sequences. (Running on oeis4.)