A257847 a(n) = floor(n/7) * (n mod 7).
0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 0, 2, 4, 6, 8, 10, 12, 0, 3, 6, 9, 12, 15, 18, 0, 4, 8, 12, 16, 20, 24, 0, 5, 10, 15, 20, 25, 30, 0, 6, 12, 18, 24, 30, 36, 0, 7, 14, 21, 28, 35, 42, 0, 8, 16, 24, 32, 40, 48, 0, 9, 18, 27, 36, 45, 54, 0, 10, 20
Offset: 0
Links
- Colin Barker, Table of n, a(n) for n = 0..1000
- Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,2,0,0,0,0,0,0,-1).
Programs
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Mathematica
Table[Floor[n/7]Mod[n,7],{n,0,80}] (* Harvey P. Dale, Nov 12 2022 *) -
PARI
a(n,b=7)=(n=divrem(n,b))[1]*n[2]
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PARI
concat([0,0,0,0,0,0,0,0], Vec(x^8*(6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^6+x^5+x^4+x^3+x^2+x+1)^2) + O(x^100))) \\ Colin Barker, May 11 2015
Formula
a(n) = 2*a(n-7)-a(n-14). - Colin Barker, May 11 2015
G.f.: x^8*(6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^6+x^5+x^4+x^3+x^2+x+1)^2). - Colin Barker, May 11 2015
Comments