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 A079612 Largest number m such that a^n == 1 (mod m) whenever a is coprime to m. 8
 2, 24, 2, 240, 2, 504, 2, 480, 2, 264, 2, 65520, 2, 24, 2, 16320, 2, 28728, 2, 13200, 2, 552, 2, 131040, 2, 24, 2, 6960, 2, 171864, 2, 32640, 2, 24, 2, 138181680, 2, 24, 2, 1082400, 2, 151704, 2, 5520, 2, 1128, 2, 4455360, 2, 264, 2, 12720, 2, 86184, 2, 13920 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(m) divides the Jordan function J_m(n) for all n except when n is a prime dividing a(m) or m=2, n=4; it is the largest number dividing all but finitely many values of J_m(n). For m > 0, a(m) also divides Sum_{k=1}^n J_m(k) for n >= the largest exceptional value. - Franklin T. Adams-Watters, Dec 10 2005 The numbers m with this property are the divisors of a(n) that are not divisors of a(r) for r 1, a(n) = 2*A075180(n-1). (End) PROG (PARI) a(n) = {if (n%2, 2, res = 1; forprime(p=2, n+1, if (!(n % (p-1)), t = valuation(n, p); if (p==2, if (t, res *= p^(t+2)), res *= p^(t+1)); ); ); res; ); } \\ Michel Marcus, May 12 2018 CROSSREFS Cf. A006863 (bisection except for initial term); A059379 (Jordan function). Cf. A075180, A115000, A115001, A115002, A115003. Cf. A143407, A143408, A185633, A322315. Sequence in context: A171636 A270562 A100816 * A329263 A227477 A066585 Adjacent sequences:  A079609 A079610 A079611 * A079613 A079614 A079615 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 29 2003 EXTENSIONS Edited by Franklin T. Adams-Watters, Dec 10 2005 Definition corrected by T. D. Noe, Aug 13 2008 Rather arbitrary term a(0) removed by Max Alekseyev, May 27 2010 STATUS approved

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Last modified April 8 18:47 EDT 2020. Contains 333323 sequences. (Running on oeis4.)