This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A235988 Sum of the partition parts of 3n into 3 parts. 10
 3, 18, 63, 144, 285, 486, 777, 1152, 1647, 2250, 3003, 3888, 4953, 6174, 7605, 9216, 11067, 13122, 15447, 18000, 20853, 23958, 27393, 31104, 35175, 39546, 44307, 49392, 54897, 60750, 67053, 73728, 80883, 88434, 96495, 104976, 113997, 123462, 133497, 144000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. C. Greubel, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (2,1,-4,1,2,-1). FORMULA a(n) = 3*n^3 - 3*n*floor(n^2/4). a(n) = 3n * A077043(n). a(n) = a(n-1) + 3*A077043(n-1) + A001651(n) + A093353(3n-2). From Colin Barker, Jan 18 2014: (Start) a(n) = (3*n*(1-(-1)^n+6*n^2))/8. G.f.: 3*x*(x^4+4*x^3+8*x^2+4*x+1) / ((x-1)^4*(x+1)^2). (End) a(n) = 2*a(n-1) + a(n-2) - 4*a(n-3) + a(n-4) + 2*a(n-5) - a(n-6) for n > 6. - Wesley Ivan Hurt, Nov 15 2015 EXAMPLE a(2) = 18; 3(2) = 6 has 3 partitions into 3 parts: (4, 1, 1), (3, 2, 1), and (2, 2, 2). The sum of the parts is 18. MAPLE A235988:=n->3*n^3 - 3*n*floor(n^2/4); seq(A235988(n), n=1..100); MATHEMATICA Table[3 n^3 - 3 n*Floor[n^2/4], {n, 100}] (* or *) CoefficientList[ Series[3*x*(x^4 + 4*x^3 + 8*x^2 + 4*x + 1)/((x - 1)^4*(x + 1)^2), {x, 0, 30}], x] LinearRecurrence[{2, 1, -4, 1, 2, -1}, {3, 18, 63, 144, 285, 486}, 40] (* Harvey P. Dale, May 17 2018 *) PROG (PARI) a(n)=3*n^3 - n^2\4*3*n \\ Charles R Greathouse IV, Oct 07 2015 (PARI) x='x+O('x^50); Vec(3*x*(x^4+4*x^3+8*x^2+4*x+1)/((x-1)^4*(x+1)^2)) \\ Altug Alkan, Nov 01 2015 (MAGMA) [3*n^3-3*n*Floor(n^2/4): n in [1..100]]; // Wesley Ivan Hurt, Nov 01 2015 (MAGMA) [3*n*(1-(-1)^n+6*n^2)/8: n in [1..40]]; // Vincenzo Librandi, Nov 18 2015 CROSSREFS Cf. A001651, A077043, A093353. Sequence in context: A299031 A210366 A000648 * A253942 A317404 A110689 Adjacent sequences:  A235985 A235986 A235987 * A235989 A235990 A235991 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Jan 17 2014 EXTENSIONS a(165) in b-file corrected by Andrew Howroyd, Feb 21 2018 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 July 16 04:26 EDT 2019. Contains 325064 sequences. (Running on oeis4.)