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 A111694 a(1) = 1+2-3 = 0, a(2) = 4+5+6-7 = 8, a(3) = 8+9+10+11-12 = 26, a(4) = 13+14+15+16+17-18 = 57, ... 2
 0, 8, 26, 57, 104, 170, 258, 371, 512, 684, 890, 1133, 1416, 1742, 2114, 2535, 3008, 3536, 4122, 4769, 5480, 6258, 7106, 8027, 9024, 10100, 11258, 12501, 13832, 15254, 16770, 18383, 20096, 21912, 23834, 25865, 28008, 30266, 32642, 35139, 37760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 FORMULA a(n) = (n^3 + 4n^2 - 3n - 2)/2. G.f.: x^2*(x-2)*(x-4)/(1-x)^4. [Colin Barker, Mar 18 2012] MAPLE seq(sum(j, j=binomial(n+1, 2)+n-1..binomial(n+2, 2)+n-2) - binomial(n+2, 2)-n+1, n=1..50); (Deutsch) MATHEMATICA Table[(n^3 + 4n^2 - 3n - 2)/2, {n, 41}] (* Robert G. Wilson v *) PROG (MAGMA) [(n^3 + 4*n^2 - 3*n - 2)/2: n in [1..60]]; // Vincenzo Librandi, May 21 2011 CROSSREFS Cf. A034856. Sequence in context: A085690 A005897 A215097 * A129111 A002413 A218325 Adjacent sequences:  A111691 A111692 A111693 * A111695 A111696 A111697 KEYWORD nonn,easy AUTHOR Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 17 2005 EXTENSIONS Edited and extended by Emeric Deutsch and Robert G. Wilson v, Aug 27 2005 STATUS approved

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