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 A166146 a(n) = (7*n^2 + 7*n - 12)/2. 3
 1, 15, 36, 64, 99, 141, 190, 246, 309, 379, 456, 540, 631, 729, 834, 946, 1065, 1191, 1324, 1464, 1611, 1765, 1926, 2094, 2269, 2451, 2640, 2836, 3039, 3249, 3466, 3690, 3921, 4159, 4404, 4656, 4915, 5181, 5454, 5734, 6021, 6315, 6616, 6924, 7239, 7561 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = a(n-1) + 7n, a(1)=1. a(n) = -6 + (7/2)*n^2 + (7/2)*n, a(1)=1. - Paolo P. Lava, Nov 10 2009 From Harvey P. Dale, Nov 01 2011: (Start) a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3), a(1)=1, a(2)=15, a(3)=36. G.f.: (6*x^2-12*x-1)/(x-1)^3. (End) E.g.f.: (1/2)*((-12 + 14*x + 7*x^2)*exp(x) + 12). - G. C. Greubel, Apr 26 2016 MATHEMATICA RecurrenceTable[{a[1]==1, a[n]==a[n-1]+7n}, a, {n, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 15, 36}, 50] (* Harvey P. Dale, Nov 01 2011 *) Table[(7 n^2 + 7 n - 12)/2, {n, 46}] (* Michael De Vlieger, Apr 27 2016 *) PROG (PARI) a(n)=7*n*(n+1)/2-6 \\ Charles R Greathouse IV, Jan 11 2012 CROSSREFS Sequence in context: A224719 A033709 A067707 * A229235 A346881 A293156 Adjacent sequences:  A166143 A166144 A166145 * A166147 A166148 A166149 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Oct 08 2009 EXTENSIONS a(35) corrected by Harvey P. Dale, Nov 01 2011 STATUS approved

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Last modified September 17 16:32 EDT 2021. Contains 347487 sequences. (Running on oeis4.)