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 A038138 Order of n (mod 7). 0
 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0, 1, 3, 6, 3, 6, 2, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..105. Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,1). FORMULA G.f.: x*(1 + 3*x + 6*x^2 + 3*x^3 + 6*x^4 + 2*x^5)/(1 - x^7). - Bruno Berselli, Mar 22 2016 a(n) = -(35*(n mod 7)^6 - 603*(n mod 7)^5 + 3860*(n mod 7)^4 - 11235*(n mod 7)^3 + 14465*(n mod 7)^2 - 6882*(n mod 7))/360. - Luce ETIENNE, Oct 20 2017 a(n) = (1/7)*(3*(n mod 7) + 5*((n+1) mod 7) - 2*((n+2) mod 7) + 4*((n+3) mod 7) - 2*((n+4) mod 7) - ((n+5) mod 7)). - Paolo P. Lava, Oct 23 2017 MATHEMATICA ReplacePart[Table[MultiplicativeOrder[n, 7], {n, 105}], List /@ Range[7, 105, 7] -> 0] (* Alonso del Arte, Mar 23 2016 *) PadRight[{}, 120, {0, 1, 3, 6, 3, 6, 2}] (* Harvey P. Dale, Apr 26 2020 *) PROG (Magma) [Modorder(n, 7): n in [0..110]]; // Bruno Berselli, Mar 22 2016 (PARI) a(n) = if (n % 7, znorder(Mod(n, 7)), 0); \\ Michel Marcus, Mar 22 2016 (PARI) x='x+O('x^200); concat(0, Vec(x*(1+3*x+6*x^2+3*x^3+6*x^4+2*x^5)/(1-x^7))) \\ Altug Alkan, Mar 23 2016 CROSSREFS Cf. A010876, A218256. Sequence in context: A151865 A124860 A182412 * A010704 A338947 A323503 Adjacent sequences: A038135 A038136 A038137 * A038139 A038140 A038141 KEYWORD nonn,easy AUTHOR Felice Russo EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), Apr 04 2000 STATUS approved

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Last modified December 11 11:25 EST 2023. Contains 367724 sequences. (Running on oeis4.)