A257846 a(n) = floor(n/6) * (n mod 6).

0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 0, 2, 4, 6, 8, 10, 0, 3, 6, 9, 12, 15, 0, 4, 8, 12, 16, 20, 0, 5, 10, 15, 20, 25, 0, 6, 12, 18, 24, 30, 0, 7, 14, 21, 28, 35, 0, 8, 16, 24, 32, 40, 0, 9, 18, 27, 36, 45, 0, 10, 20, 30, 40, 50, 0, 11, 22, 33, 44, 55, 0, 12, 24

Offset

0,9

Comments

Equivalently, write n in base 6, multiply the last digit by the number with its last digit removed.

Links

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

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

Formula

a(n) = 2*a(n-6)-a(n-12). - Colin Barker, May 11 2015

G.f.: x^7*(5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2-x+1)^2*(x^2+x+1)^2). - Colin Barker, May 11 2015

Mathematica

Table[Floor[n/6]*Mod[n, 6], {n, 120}] (* Michael De Vlieger, May 11 2015 *)

Prog

(PARI) a(n, b=6)=(n=divrem(n, b))[1]*n[2]
(PARI) concat([0, 0, 0, 0, 0, 0, 0], Vec(x^7*(5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2-x+1)^2*(x^2+x+1)^2) + O(x^100))) \\ Colin Barker, May 11 2015

Crossrefs

Cf. A142150 (the base 2 analog), A115273, A257844 - A257850.

Sequence in context: A309957 A365459 A220660 * A203572 A195829 A095874

Adjacent sequences: A257843 A257844 A257845 * A257847 A257848 A257849

Keyword

nonn,easy

Author

M. F. Hasler, May 10 2015

Status

approved