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 A006503 a(n) = n*(n+1)*(n+8)/6. (Formerly M2835) 14
 0, 3, 10, 22, 40, 65, 98, 140, 192, 255, 330, 418, 520, 637, 770, 920, 1088, 1275, 1482, 1710, 1960, 2233, 2530, 2852, 3200, 3575, 3978, 4410, 4872, 5365, 5890, 6448, 7040, 7667, 8330, 9030, 9768, 10545, 11362, 12220, 13120, 14063, 15050, 16082, 17160, 18285 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS If Y is a 3-subset of an n-set X then, for n>=4, a(n-4) is the number of 3-subsets of X having at most one element in common with Y. - Milan Janjic, Nov 23 2007 The coefficient of x^3 in (1-x-x^2)^{-n} is the coefficient of x^3 in (1+x+2x^2+3x^3)^n. Using the multinomial theorem one then finds that a(n)=n(n+1)(n+8)/3!. - Sergio Falcon, May 22 2008 REFERENCES A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS G. C. Greubel, Table of n, a(n) for n = 0..5000 G. E. Bergum and V. E. Hoggatt, Jr., Numerator polynomial coefficient array for the convolved Fibonacci sequence, Fib. Quart., 14 (1976), 43-44. (Annotated scanned copy) G. E. Bergum and V. E. Hoggatt, Jr., Numerator polynomial coefficient array for the convolved Fibonacci sequence, Fib. Quart., 14 (1976), 43-48. M. Janjic, Hessenberg Matrices and Integer Sequences , J. Int. Seq. 13 (2010) # 10.7.8, section 3. P. Moree, Convoluted convolved Fibonacci numbers, arXiv:math/0311205 [math.CO], 2003. P. Moree, Convoluted Convolved Fibonacci Numbers, Journal of Integer Sequences, Vol. 7 (2004), Article 04.2.2. Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992. Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992. Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA a(n) = n*(n+1)*(n+8)/6. G.f.: x*(3-2*x)/(1-x)^4. a(n) = A000292(n) + A002378(n). - Reinhard Zumkeller, Sep 24 2008 a(0)=0, a(1)=3, a(2)=10, a(3)=22, a(n)=4*a(n-1)-6*a(n-2)+ 4*a(n-3)- a(n-4). - Harvey P. Dale, Jan 27 2016 MAPLE A006503:=-(-3+2*z)/(z-1)**4; # [Simon Plouffe in his 1992 dissertation.] MATHEMATICA Clear["Global`*"] a[n_] := n(n + 1)(n + 8)/3! Do[Print[n, " ", a[n]], {n, 1, 25}] (* Sergio Falcon, May 22 2008 *) Table[n(n+1)(n+8)/6, {n, 0, 50}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {0, 3, 10, 22}, 50] (* Harvey P. Dale, Jan 27 2016 *) PROG (PARI) x='x+O('x^50); concat(, Vec(x*(3-2*x)/(1-x)^4)) \\ G. C. Greubel, May 11 2017 CROSSREFS a(n) = A095660(n+2, 3): fourth column of (1, 3)-Pascal triangle. Cf. A000027, A000096, A006504. Row n=3 of A144064. Sequence in context: A326124 A122795 A140066 * A248851 A023554 A294414 Adjacent sequences:  A006500 A006501 A006502 * A006504 A006505 A006506 KEYWORD nonn,easy AUTHOR EXTENSIONS Better description from Jeffrey Shallit, Aug 1995 STATUS approved

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Last modified July 13 22:21 EDT 2020. Contains 335716 sequences. (Running on oeis4.)