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A115266 Row sums of correlation triangle for floor((n+3)/3). 1
1, 2, 4, 8, 13, 20, 31, 44, 61, 84, 111, 144, 186, 234, 291, 360, 438, 528, 634, 752, 886, 1040, 1210, 1400, 1615, 1850, 2110, 2400, 2715, 3060, 3441, 3852, 4299, 4788, 5313, 5880, 6496, 7154, 7861, 8624, 9436, 10304, 11236, 12224, 13276, 14400, 15588 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Row sums of number triangle A115265.

LINKS

Table of n, a(n) for n=0..46.

Index entries for linear recurrences with constant coefficients, signature (2,0,0,-3,0,3,0,0,-2,1).

FORMULA

G.f.: (1+x+x^2)^2/((1-x^3)^4*(1-x^2)); a(n)=sum{k=0..n, sum{j=0..n, [j<=k]*floor((k-j+3)/3)*[j<=n-k]*floor((n-k-j+3)/3)}}.

MATHEMATICA

T[n_, k_] := Sum[Boole[j <= k] * Floor[(k - j + 3)/3] * Boole[j <= n - k] * Floor[(n - k - j + 3)/3], {j, 0, n}]; a[n_] := Sum[T[n, k], {k, 0, n}]; Table[a[n], {n, 0, 46}] (* Jean-Fran├žois Alcover, Jul 15 2017 *)

CROSSREFS

Sequence in context: A164466 A164487 A130840 * A164508 A308094 A292774

Adjacent sequences:  A115263 A115264 A115265 * A115267 A115268 A115269

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jan 18 2006

STATUS

approved

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Last modified September 27 17:05 EDT 2021. Contains 347693 sequences. (Running on oeis4.)