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A016051 Numbers of the form 9n+3 or 9n+6. 2
3, 6, 12, 15, 21, 24, 30, 33, 39, 42, 48, 51, 57, 60, 66, 69, 75, 78, 84, 87, 93, 96, 102, 105, 111, 114, 120, 123, 129, 132, 138, 141, 147, 150, 156, 159, 165, 168, 174, 177, 183, 186, 192, 195, 201, 204, 210, 213, 219, 222, 228, 231, 237, 240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n+1) = a(n) + its digital root.

LINKS

Table of n, a(n) for n=1..54.

FORMULA

a(n)= +a(n-1) +a(n-2) -a(n-3) = 9*n/2-9/4-3*(-1)^n/4. G.f: 3*x*(1+x+x^2)/((1+x)*(x-1)^2) [From R. J. Mathar, Dec 16 2009]

a(n)=9*(n-1)-a(n-1) (with a(1)=3) [From Vincenzo Librandi, Nov 19 2010]

CROSSREFS

Equals 3*A001651.

Subsequence of A145204. [From Reinhard Zumkeller, Oct 04 2008]

Sequence in context: A067759 A191267 A145204 * A070790 A114614 A016052

Adjacent sequences:  A016048 A016049 A016050 * A016052 A016053 A016054

KEYWORD

nonn,base,easy

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified May 23 14:50 EDT 2013. Contains 225605 sequences.