A281258 Digital root of n*(n+1)*(n+2)/2.

0, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9, 3, 3, 3, 6, 6, 6, 9, 9, 9

Offset

0,2

Comments

Also zero together with period 9: repeat [3, 3, 3, 6, 6, 6, 9, 9, 9].

Also the decimal expansion of 334001/1001001.

Links

Table of n, a(n) for n=0..117.

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

Formula

a(n) = A010888(A027480(n)).

From Stefano Spezia, Aug 30 2022: (Start)

G.f.: 3*x*(1 + 2*x^3 + 3*x^6)/((1 - x)*(1 + x^3 + x^6)).

a(n) = a(n-1) - a(n-3) + a(n-4) - a(n-6) + a(n-7) for n > 7. (End)

Mathematica

PadRight[{0}, 120, {9, 3, 3, 3, 6, 6, 6, 9, 9}] (* Harvey P. Dale, Mar 22 2018 *)

Crossrefs

Cf. A010888, A027480.

Sequence in context: A073080 A171601 A057944 * A080607 A013322 A211534

Adjacent sequences: A281255 A281256 A281257 * A281259 A281260 A281261

Keyword

nonn,base,easy

Author

Peter M. Chema, Jan 18 2017

Status

approved