

A115273


a(n) = floor(n/3)*(n mod 3).


10



0, 0, 0, 0, 1, 2, 0, 2, 4, 0, 3, 6, 0, 4, 8, 0, 5, 10, 0, 6, 12, 0, 7, 14, 0, 8, 16, 0, 9, 18, 0, 10, 20, 0, 11, 22, 0, 12, 24, 0, 13, 26, 0, 14, 28, 0, 15, 30, 0, 16, 32, 0, 17, 34, 0, 18, 36, 0, 19, 38, 0, 20, 40, 0, 21, 42, 0, 22, 44, 0, 23, 46, 0, 24, 48, 0, 25, 50, 0, 26, 52, 0, 27, 54, 0, 28, 56
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OFFSET

0,6


COMMENTS

Three arithmetic progressions interlaced: a(1)=1,2,0 and d=a(n+1)a(n)=1,2,0. Cf. A115274(n) = n+a(n), n=1,2,3,...


LINKS



FORMULA

a(3k+1) = k, a(3k+2) = 2k, a(3k+3) = 0, k=1, 2, ...
G.f.: x^4*(2*x+1) / ((x1)^2*(x^2+x+1)^2).  Colin Barker, May 11 2015


MATHEMATICA

Table[Floor[n/3]*Mod[n, 3], {n, 0, 104}] \\ Extended to offset 0 by M. F. Hasler, May 11 2015


PROG

(PARI) a(n, b=3)=(n=divrem(n, b))[1]*n[2] \\ M. F. Hasler, May 10 2015
(Python)
from math import prod


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS

a(0)a(3) and crossreferences added by M. F. Hasler, May 11 2015


STATUS

approved



