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 A084967 Multiples of 5 whose GCD with 6 is 1. 25
 5, 25, 35, 55, 65, 85, 95, 115, 125, 145, 155, 175, 185, 205, 215, 235, 245, 265, 275, 295, 305, 325, 335, 355, 365, 385, 395, 415, 425, 445, 455, 475, 485, 505, 515, 535, 545, 565, 575, 595, 605, 625, 635, 655, 665, 685, 695, 715, 725, 745, 755, 775, 785 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Third row of A083140. Positions of 5 in A020639. - Zak Seidov, Apr 29 2015 LINKS Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA Numbers of the form 5k for which gcd(5k, 6) = 1. a(n) = 5*A007310(n). - Adriano Caroli, Oct 03 2010 From Colin Barker, Feb 24 2013: (Start) a(n) = 5*(-3 + (-1)^n + 6*n)/2. a(n) = a(n-1) + a(n-2) - a(n-3). G.f.: 5*x*(x^2+4*x+1) / ((x-1)^2*(x+1)). (End) Lim_{n->infinity} a(n)/n = A038111(3)/A038110(3) = 15. - Vladimir Shevelev, Jan 20 2015 For n > 2, a(n) = a(n-2) + 30. - Zak Seidov, Apr 29 2015 a(n) = A007310(A273669(n)). - Antti Karttunen, May 20 2017 MATHEMATICA 5Select[ Range[160], GCD[ #, 2*3] == 1 & ] Select[Range[5, 785, 10], Mod[#, 3] > 0 &] (* Zak Seidov, Apr 29 2015 *) a[1] = 5; a[n_] := a[n] = a[n - 1] + 10*(2 - Mod[n, 2]); Table[a[n], {n, 50}] (* Zak Seidov, Apr 29 2015 *) PROG (PARI) is(n)=n%5==0 && gcd(n, 6)==1 \\ Charles R Greathouse IV, Nov 19 2014 (PARI) list(lim)=5*select(k->gcd(n, 6)==1, [1..lim\5]) \\ Charles R Greathouse IV, Nov 19 2014 CROSSREFS Cf. A083140, A063149, A007310 (5-rough numbers), A273669. Cf. A020639. - Zak Seidov, Apr 29 2015 Sequence in context: A029475 A332657 A070391 * A249827 A279541 A070390 Adjacent sequences:  A084964 A084965 A084966 * A084968 A084969 A084970 KEYWORD nonn,easy AUTHOR Robert G. Wilson v, Jun 15 2003 STATUS approved

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Last modified October 23 20:46 EDT 2020. Contains 337975 sequences. (Running on oeis4.)