A287209 - OEIS

A287209

a(1)=4, a(2)=5, a(n) = sum of digits of a(n-1) + sum of digits of a(n-2), n>=3.

4, 5, 9, 14, 14, 10, 6, 7, 13, 11, 6, 8, 14, 13, 9, 13, 13, 8, 12, 11, 5, 7, 12, 10, 4, 5, 9, 14, 14, 10, 6, 7, 13, 11, 6, 8, 14, 13, 9, 13, 13, 8, 12, 11, 5, 7, 12, 10, 4, 5, 9, 14, 14, 10, 6, 7, 13, 11, 6, 8, 14, 13, 9, 13, 13, 8, 12, 11, 5, 7, 12, 10, 4, 5, 9, 14, 14, 10, 6, 7, 13, 11, 6, 8

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OFFSET

1,1

COMMENTS

Digital sum analog in base 10 of the Fibonacci recurrence starting with 4,5.

The sequence is periodic from n=1 with period 24.

LINKS

Table of n, a(n) for n=1..84.

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

FORMULA

a(n) = a(n-1) + a(n-2) - 9*(floor(a(n-1)/10)+floor(a(n-2)/10)).

MATHEMATICA

a[n_] := a[n] = If[n <= 2, n + 3, Total@ IntegerDigits[a[n - 1]] + Total@ IntegerDigits[a[n - 2]]]; Array[a, 84] (* Michael De Vlieger, May 22 2017 *)

CROSSREFS

Cf. A000285, A283428.

Sequence in context: A318980 A226622 A332302 * A038099 A243166 A363284

Adjacent sequences: A287206 A287207 A287208 * A287210 A287211 A287212

KEYWORD

nonn,base

AUTHOR

Enrique Navarrete, May 21 2017

STATUS

approved