|
|
A175287
|
|
Partial sums of ceiling(n^2/4).
|
|
4
|
|
|
0, 1, 2, 5, 9, 16, 25, 38, 54, 75, 100, 131, 167, 210, 259, 316, 380, 453, 534, 625, 725, 836, 957, 1090, 1234, 1391, 1560, 1743, 1939, 2150, 2375, 2616, 2872, 3145, 3434, 3741, 4065, 4408, 4769, 5150, 5550, 5971, 6412, 6875, 7359, 7866, 8395, 8948, 9524, 10125, 10750
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
COMMENTS
|
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
|
|
LINKS
|
|
|
FORMULA
|
a(n) = round((2*n+1)*(2*n^2+2*n+9)/48).
a(n) = floor((n+1)*(2*n^2+n+9)/24).
a(n) = ceiling((2*n^3+3*n^2+10*n)/24).
a(n) = round((2*n^3+3*n^2+10*n)/24).
a(n) = a(n-4)+n^2-3*n+5 , n>3.
G.f.: x*(1-x+x^2) / ( (1+x)*(x-1)^4 ).
a(n) = (2*n*(2*n^2+3*n+10)-9*(-1)^n+9)/48. - Bruno Berselli, Dec 03 2010
|
|
EXAMPLE
|
a(4) = ceil(0/4)+ceil(1/4)+ceil(4/4)+ceil(9/4)+ceil(16/4) = 0+1+1+3+4=9.
|
|
MAPLE
|
a:= n-> round((2*n^(3)+3*n^(2)+10*n)/24): seq(a(n), n=0..20);
|
|
MATHEMATICA
|
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 *)
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 *)
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 *)
|
|
PROG
|
(Magma) [Floor((n+1)*(2*n^2+n+9)/24): n in [0..60]]; // Vincenzo Librandi, Jun 22 2011
(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
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|