OFFSET
0,6
LINKS
Mircea Merca, Inequalities and Identities Involving Sums of Integer Functions J. Integer Sequences, Vol. 14 (2011), Article 11.9.1.
FORMULA
a(n) = sum(k=0..n,floor(k^2/10)).
a(n) = a(n-10)+(n-5)^2+n-1 , n>9.
G.f.: x^4*(1+x^4) / ( (1+x)*(x^4+x^3+x^2+x+1)*(x^4-x^3+x^2-x+1)*(x-1)^4 ). [R. J. Mathar, Nov 24 2010]
a(n)= +3*a(n-1) -3*a(n-2) +a(n-3) +a(n-10) -3*a(n-11) +3*a(n-12) -a(n-13). [R. J. Mathar, Nov 24 2010]
EXAMPLE
a(9) = 0+0+0+0+1+2+3+4+6+8 = 24
MATHEMATICA
Accumulate[Floor[Range[0, 50]^2/10]] (* Harvey P. Dale, May 31 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Mircea Merca, Nov 24 2010
STATUS
approved