A256676 - OEIS

A256676

Digital roots of centered 11-gonal numbers (A069125).

1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3, 4, 7, 3, 1, 1, 3, 7, 4, 3

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OFFSET

1,2

COMMENTS

The sequence is periodic with period 9.

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

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

FORMULA

a(n) = A010888(A069125(n)).

a(n) = a(n-9).

G.f.: -x*(x^8+3*x^7+7*x^6+4*x^5+3*x^4+4*x^3+7*x^2+3*x+1) / ((x-1)*(x^2+x+1)*(x^6+x^3+1)).

EXAMPLE

a(3) = 7 because the 3rd centered 11-gonal number is 34, the digital root of which is 7.

MATHEMATICA

PadRight[{}, 100, {1, 3, 7, 4, 3, 4, 7, 3, 1}] (* Vincenzo Librandi, Apr 08 2015 *)

LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 0, 1}, {1, 3, 7, 4, 3, 4, 7, 3, 1}, 86] (* Ray Chandler, Aug 26 2015 *)

PROG

(PARI) m=11; vector(200, n, (m*n*(n-1)/2)%9+1)

(Magma) &cat[[1, 3, 7, 4, 3, 4, 7, 3, 1]: n in [0..10] ]; // Vincenzo Librandi, Apr 08 2015

CROSSREFS

Cf. A010888, A069125.

Sequence in context: A367264 A266273 A341605 * A349010 A267412 A087941

Adjacent sequences: A256673 A256674 A256675 * A256677 A256678 A256679

KEYWORD

nonn,base,easy

AUTHOR

Colin Barker, Apr 07 2015

STATUS

approved