The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A182665 Greatest x < n such that n divides x*(x-1). 1
 0, 1, 1, 1, 1, 4, 1, 1, 1, 6, 1, 9, 1, 8, 10, 1, 1, 10, 1, 16, 15, 12, 1, 16, 1, 14, 1, 21, 1, 25, 1, 1, 22, 18, 21, 28, 1, 20, 27, 25, 1, 36, 1, 33, 36, 24, 1, 33, 1, 26, 34, 40, 1, 28, 45, 49, 39, 30, 1, 45, 1, 32, 36, 1, 40, 55, 1, 52, 46, 56, 1, 64, 1, 38, 51, 57, 56, 66, 1, 65, 1, 42, 1, 64, 51, 44, 58, 56, 1, 81, 78, 69, 63, 48, 76, 64, 1, 50, 55 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS a(n) = 1 iff n is in A246655. - Robert Israel, Jan 13 2015 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(6) = 4 because 6 divides 4*3=12 but does not divide 5*4=20. MAPLE A:= proc(n)        max(map(u -> u*modp(1/u, n/u),                       map(t -> mul(s[1]^s[2], s = t),                           combinat[powerset](ifactors(n)[2]))))      end proc; seq(A(n), n=1..100); MATHEMATICA a[n_] := Module[{x}, Max[x /. {ToRules[Reduce[Mod[x*(x-1), n] == 0 && Mod[x*(x+1), n] != 0, x, Integers] /. C[_] -> 0]}]]; a[1] = 0; a[2] = 1; Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Mar 04 2014 *) CROSSREFS Sequence in context: A306264 A321647 A323410 * A131299 A073937 A074058 Adjacent sequences:  A182662 A182663 A182664 * A182666 A182667 A182668 KEYWORD nonn,easy AUTHOR Robert Israel, Dec 23 2012 STATUS approved

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

Last modified May 26 13:49 EDT 2020. Contains 334626 sequences. (Running on oeis4.)