A259181 - OEIS

A259181

a(n) = n*(n+1)*(n+2)*(n+3)*(2*n^2+6*n+7)/360.

0, 1, 9, 43, 147, 406, 966, 2058, 4026, 7359, 12727, 21021, 33397, 51324, 76636, 111588, 158916, 221901, 304437, 411103, 547239, 719026, 933570, 1198990, 1524510, 1920555, 2398851, 2972529, 3656233, 4466232, 5420536, 6539016, 7843528, 9358041, 11108769

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OFFSET

0,3

COMMENTS

After 0, second bisection of A129548.

This sequence is also the total number of squares of all sizes in i X i subsquares in an n X n grid, whereas A000330 simply gives the number of all sizes of squares in an n X n grid. See illustrations.

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Luce ETIENNE, illustration of initial terms

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).

FORMULA

a(n) = (1/6)*Sum_{i=0..n} (i+1)*(i+2)*(2*i+3)*(n-i)^2.

a(n) = Sum_{i=0..n} A000290(n-i)*A000330(i+1).

G.f.: x*(1 + x)^2 / (1 - x)^7. - Colin Barker, Nov 08 2015

a(n) = (A000539(n+1) - A000217(n+1))/30. - Yasser Arath Chavez Reyes, Feb 24 2024

EXAMPLE

a(0) = 0; a(1) = 1*1; a(2) = 4*1+1*5 = 9; a(3) = 9*1+4*5+1*14 = 43.

PROG