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 A005586 a(n) = n(n+4)(n+5)/6. (Formerly M3841) 18
 0, 5, 14, 28, 48, 75, 110, 154, 208, 273, 350, 440, 544, 663, 798, 950, 1120, 1309, 1518, 1748, 2000, 2275, 2574, 2898, 3248, 3625, 4030, 4464, 4928, 5423, 5950, 6510, 7104, 7733, 8398, 9100, 9840, 10619, 11438, 12298, 13200, 14145, 15134, 16168, 17248 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Number of walks on square lattice. Number of standard tableaux of shape (n+2,3) (n >= 1). - Emeric Deutsch, May 20 2004 Number of left factors of Dyck paths from (0,0) to (n+5,n-1). E.g. a(1)=5 because we have UDUDUD, UDUUDD, UUDDUD, UUDUDD and UUUDDD, where U=(1,1) and D=(1,-1). - Emeric Deutsch, Jan 25 2005 Column 4 of Catalan triangle A009766. - Zerinvary Lajos, Nov 25 2006 Sum of first n triangular numbers minus next triangular number. - Vladimir Joseph Stephan Orlovsky, Oct 13 2009 a(n) = A214292(n+4,2). - Reinhard Zumkeller, Jul 12 2012 REFERENCES M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 796. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy]. R. K. Guy, Letter to N. J. A. Sloane, Feb 1988 R. K. Guy, Catwalks, Sandsteps and Pascal Pyramids, J. Integer Seqs., Vol. 3 (2000), #00.1.6 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 G.f.: x * (5 - 6*x + 2*x^2) / (1 - x)^4. E.g.f.: (5*x + 2*x^2 + x^3/6) * exp(x). - Michael Somos, Apr 13 2007 Let t(n) = n*(n+1)/2, te(n) = (n+1)*(n+2)*(n+3)/6. Then a(n-4) = -2*t(n) + te(n-1), e.g., a(2) = -2*t(6) + te(5) = -2*21 + 56 = 14, where te(n) are the tetrahedral numbers A000292 and t(n) are the triangular numbers A000217. - Jon Perry, Jul 23 2003 a(n) = C(5+n, 3)-C(5+n, 2). - Zerinvary Lajos, Jan 09 2006 a(n) = C(n,3) - C(n,1), n>=4. - Zerinvary Lajos, Nov 25 2006 a(n) = - A005581(-4-n) for all n in Z. - Michael Somos, Apr 13 2007 EXAMPLE G.f. = 5*x + 14*x^2 + 28*x^3 + 48*x^4 + 75*x^5 + 110*x^6 + 154*x^7 + ... MAPLE [seq(binomial(n, 3 )-binomial(n, 1), n=4..48)]; # Zerinvary Lajos, Nov 25 2006 a:=n->sum ((j-3)*j/2, j=0..n): seq(a(n), n=4..48); # Zerinvary Lajos, Dec 17 2006 A005586:=z*(5-6*z+2*z**2)/(z-1)**4; # conjectured by Simon Plouffe in his 1992 dissertation seq(sum(binomial(n, m), m=1..3)-n^2, n=5..49); # Zerinvary Lajos, Jun 19 2008 MATHEMATICA Clear[lst, n, a, f]; f[n_]:=n*(n+1)/2; a=0; lst={}; Do[a+=f[n]; AppendTo[lst, a-f[n+1]], {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 13 2009 *) CoefficientList[Series[x (5 - 6 x + 2 x^2) / (1 - x)^4, {x, 0, 50}], x] (* Vincenzo Librandi, Jun 09 2013 *) Table[(n(n+4)(n+5))/6, {n, 0, 50}] (* or *) LinearRecurrence[{4, -6, 4, -1}, {0, 5, 14, 28}, 50] (* Harvey P. Dale, Jul 14 2018 *) PROG (PARI) {a(n) = n * (n+4) * (n+5) / 6}; /* Michael Somos, Apr 13 2007 */ (MAGMA) [n*(n+4)*(n+5)/6: n in [0..50]]; // Vincenzo Librandi, Jun 09 2013 CROSSREFS Cf. A000217, A000292, A005581, A009766, A053121. a(n)=A053121(n+5,n-1). Sequence in context: A073347 A134238 A024800 * A197058 A212678 A244100 Adjacent sequences:  A005583 A005584 A005585 * A005587 A005588 A005589 KEYWORD nonn,easy AUTHOR EXTENSIONS M3842=A005555 in the 1995 EIS was the same sequence as this. More terms from Zerinvary Lajos, Jan 09 2006 STATUS approved

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Last modified January 19 06:37 EST 2020. Contains 331033 sequences. (Running on oeis4.)