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a(n) = n*(n + 1)*(n^2 - 3*n + 5)/6.
(Formerly M2839)
19

%I M2839 #50 Dec 12 2022 11:01:30

%S 0,1,3,10,30,75,161,308,540,885,1375,2046,2938,4095,5565,7400,9656,

%T 12393,15675,19570,24150,29491,35673,42780,50900,60125,70551,82278,

%U 95410,110055,126325,144336,164208,186065,210035,236250,264846,295963,329745,366340

%N a(n) = n*(n + 1)*(n^2 - 3*n + 5)/6.

%C Structured meta-pyramidal numbers, the n-th number from an n-gonal pyramidal number sequence. - James A. Record (james.record(AT)gmail.com), Nov 07 2004

%C The Gi4 triangle sums of A139600 are given by the terms of this sequence. For the definitions of the Gi4 and other triangle sums see A180662. - _Johannes W. Meijer_, Apr 29 2011

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Vincenzo Librandi, <a href="/A006484/b006484.txt">Table of n, a(n) for n = 0..1000</a>

%H D. S. Kluk and N. J. A. Sloane, <a href="/A002050/a002050_3.pdf">Correspondence, 1979</a>.

%H Simon Plouffe, <a href="https://arxiv.org/abs/0911.4975">Approximations de séries génératrices et quelques conjectures</a>, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.

%H Simon Plouffe, <a href="/A000051/a000051_2.pdf">1031 Generating Functions</a>, Appendix to Thesis, Montreal, 1992

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).

%F a(n) = (1/6)*(n^4 - 2*n^3 + 2*n^2 + 5*n). - James A. Record (james.record(AT)gmail.com), Nov 07 2004

%F a(n) = binomial(n+3,4) - 2*binomial(n+2,4) + 5*binomial(n+1,4). - _Johannes W. Meijer_, Apr 29 2011

%p A006484:=-(1-2*z+5*z**2)/(z-1)**5; # conjectured by _Simon Plouffe_ in his 1992 dissertation

%t lst={};Do[AppendTo[lst, n*(n+1)*(n^2-3*n+5)/6], {n, 0, 4!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Sep 19 2008 *)

%t Table[n(n+1) (n^2-3n+5)/6,{n,0,40}] (* _Harvey P. Dale_, May 29 2019 *)

%o (Magma) [n*(n+1)*(n^2 - 3*n + 5)/6: n in [0..50]]; // _Vincenzo Librandi_, May 16 2011

%o (PARI) a(n)=n*(n+1)*(n^2-3*n+5)/6 \\ _Charles R Greathouse IV_, Oct 18 2022

%Y Cf. other meta sequences: A100177: prism; A000447: "polar" diamond; A059722: "equatorial diamond"; A100185: anti-prism; A100188: "polar" anti-diamond; and A100189: "equatorial" anti-diamond. Cf. A100145 for more on structured numbers.

%Y Cf. A000332.

%K nonn,easy

%O 0,3

%A Dennis S. Kluk (mathemagician(AT)ameritech.net)