A175287 - OEIS

%I #57 Mar 09 2023 20:10:48

%S 0,1,2,5,9,16,25,38,54,75,100,131,167,210,259,316,380,453,534,625,725,

%T 836,957,1090,1234,1391,1560,1743,1939,2150,2375,2616,2872,3145,3434,

%U 3741,4065,4408,4769,5150,5550,5971,6412,6875,7359,7866,8395,8948,9524,10125,10750

%N Partial sums of ceiling(n^2/4).

%C a(n) is the number of 1243-avoiding odd Grassmannian permutations of size n+1. Avoiding any of the patterns 2134, 2341, or 4123, gives the same sequence. - _Juan B. Gil_, Mar 09 2023

%H Vincenzo Librandi, <a href="/A175287/b175287.txt">Table of n, a(n) for n = 0..10000</a>

%H L. Colmenarejo, <a href="http://arxiv.org/abs/1604.00803">Combinatorics on several families of Kronecker coefficients related to plane partitions</a>, arXiv:1604.00803 [math.CO], 2016. See Table 1 p. 5.

%H Juan B. Gil and Jessica A. Tomasko, <a href="https://arxiv.org/abs/2207.12617">Pattern-avoiding even and odd Grassmannian permutations</a>, arXiv:2207.12617 [math.CO], 2022.

%H Mircea Merca, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL14/Merca/merca3.html">Inequalities and Identities Involving Sums of Integer Functions</a> J. Integer Sequences, Vol. 14 (2011), Article 11.9.1.

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,-2,3,-1).

%F a(n) = round((2*n+1)*(2*n^2+2*n+9)/48).

%F a(n) = floor((n+1)*(2*n^2+n+9)/24).

%F a(n) = ceiling((2*n^3+3*n^2+10*n)/24).

%F a(n) = round((2*n^3+3*n^2+10*n)/24).

%F a(n) = a(n-4)+n^2-3*n+5 , n>3.

%F G.f.: x*(1-x+x^2) / ( (1+x)*(x-1)^4 ).

%F a(n) = (2*n*(2*n^2+3*n+10)-9*(-1)^n+9)/48. - _Bruno Berselli_, Dec 03 2010

%e a(4) = ceil(0/4)+ceil(1/4)+ceil(4/4)+ceil(9/4)+ceil(16/4) = 0+1+1+3+4=9.

%p a:= n-> round((2*n^(3)+3*n^(2)+10*n)/24): seq(a(n), n=0..20);

%t Table[Sum[Ceiling[i^2/4], {i, 0, n}], {n, 0, 49}] (* or *) Table[(2n(2n^2 + 3n + 10) -9(-1)^n + 9)/48, {n, 0, 49}] (* _Alonso del Arte_, Dec 03 2010 *)

%t CoefficientList[Series[(x^3 - x^2 + x)/(x^5 - 3 x^4 + 2 x^3 + 2 x^2 - 3 x + 1), {x, 0, 50}], x] (* _Vincenzo Librandi_, Mar 26 2014 *)

%t Accumulate[Ceiling[Range[0,50]^2/4]] (* or *) LinearRecurrence[{3,-2,-2,3,-1},{0,1,2,5,9},60] (* _Harvey P. Dale_, Nov 19 2014 *)

%o (Magma) [Floor((n+1)*(2*n^2+n+9)/24): n in [0..60]]; // _Vincenzo Librandi_, Jun 22 2011

%o (PARI) x='x+O('x^99); concat(0, Vec((x^3-x^2+x)/ (x^5-3*x^4+2*x^3+2*x^2-3*x+1))) \\ _Altug Alkan_, Apr 05 2016

%Y Partial sums of A004652.

%Y Cf. A361272.

%K nonn,easy

%O 0,3

%A _Mircea Merca_, Dec 03 2010