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 A008381 floor(n/5)*floor((n+1)/5)*floor((n+2)/5)*floor((n+3)/5). 0

%I #5 Mar 30 2012 17:38:27

%S 0,0,0,0,0,1,1,2,4,8,16,16,24,36,54,81,81,108,144,192,256,256,320,400,

%T 500,625,625,750,900,1080,1296,1296,1512,1764,2058,2401,2401,2744,

%U 3136,3584,4096,4096,4608,5184,5832

%N floor(n/5)*floor((n+1)/5)*floor((n+2)/5)*floor((n+3)/5).

%F a(n) = A002266(n)*A008496(n+1). a(n)= +a(n-1) +4*a(n-5) -4*a(n-6) -6*a(n-10) +6*a(n-11) +4*a(n-15) -4*a(n-16) -a(n-20) +a(n-21). G.f.: x^5*(x^10-2*x^9+4*x^8-4*x^7+8*x^6-8*x^5+8*x^4-4*x^3+4*x^2-2*x+1) * (1+x)^2 / ((x^4+x^3+x^2+x+1)^4 * (1-x)^5). [From _R. J. Mathar_, Apr 16 2010]

%K nonn

%O 0,8

%A _N. J. A. Sloane_.

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Last modified February 22 06:02 EST 2024. Contains 370240 sequences. (Running on oeis4.)