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 A281258 Digital root of n*(n+1)*(n+2)/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 (list; graph; refs; listen; history; text; internal format)
 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 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

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Last modified December 6 16:00 EST 2022. Contains 358644 sequences. (Running on oeis4.)