The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A181832 The product of the positive integers <= n that are strongly prime to n. 12
 1, 1, 1, 1, 1, 3, 1, 20, 15, 35, 7, 36288, 35, 277200, 1485, 4576, 9009, 20432412000, 5005, 1097800704000, 459459, 5912192, 2834325, 2322315553259520000, 1616615, 124672148625024, 4865140665 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS k is strongly prime to n iff k is relatively prime to n and k does not divide n-1. a(n) = A001783(n) / A007955(n-1) if n > 0 and a(0) = 1. For 0 we have the empty product, giving 1. - Daniel Forgues, Aug 03 2012 From Robert G. Wilson v, Aug 04 2012: (Start) Records appear at positions 0, 5, 7, 9, 11, 13, 17, 19, 23, 29, 31, .... Except for 0 and 9, all records appear at prime positions and beginning with the sixth term, are == 0 (mod 100). There are some primes which are not records: 2, 3, 61, 73, 109, 151, 181, 193, 229, 241, 271, 313, 349, 421, 433, 463, .... Anti-records appear at positions 6, 10, 12, 14, 15, 18, 20, 24, 30, 36, 42, 48, 60, 66, 70, 78, 84, 90, 96, ..., and their values are odd. (End) LINKS Robert G. Wilson v, Table of n, a(n) for n = 0..1000 Peter Luschny, Strong coprimality. EXAMPLE a(11) = 3 * 4 * 6 * 7 * 8 * 9 = 36288. MAPLE with(numtheory): StrongCoprimes := n -> select(k->igcd(k, n)=1, {\$1..n}) minus divisors(n-1): A181832 := proc(n) local i; mul(i, i=StrongCoprimes(n)) end: coprimorial := proc(n) local i; mul(i, i=select(k->igcd(k, n)=1, [\$1..n])) end: divisorial := proc(n) local i; mul(i, i=divisors(n)) end: A181832a := n -> `if`(n=0, 1, coprimorial(n)/divisorial(n-1)): MATHEMATICA f[n_] := Times @@ Select[ Range@ n, GCD[#, n] == 1 && Mod[n - 1, #] != 0 &]; Array[f, 27, 0] (* Robert G. Wilson v, Aug 03 2012 *) CROSSREFS Cf. A181830, A181831, A181833, A181834, A181835, A181836, A001783, A007955. Sequence in context: A038455 A343890 A067802 * A139723 A030042 A045496 Adjacent sequences: A181829 A181830 A181831 * A181833 A181834 A181835 KEYWORD nonn AUTHOR Peter Luschny, Nov 17 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 7 20:05 EDT 2024. Contains 375749 sequences. (Running on oeis4.)