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 A083817 Interleaving of (1,2,3,4,5,...), (2,2,2,2,...) and (0,1,3,6,10,...). 0
 1, 2, 0, 2, 2, 1, 3, 2, 3, 4, 2, 6, 5, 2, 10, 6, 2, 15, 7, 2, 21, 8, 2, 28, 9, 2, 36, 10, 2, 45, 11, 2, 55, 12, 2, 66, 13, 2, 78, 14, 2, 91, 15, 2, 105, 16, 2, 120, 17, 2, 136, 18, 2, 153, 19, 2, 171, 20, 2, 190, 21, 2, 210, 22, 2, 231, 23, 2, 253, 24, 2, 276, 25, 2, 300, 26, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Table of n, a(n) for n=0..76. Index entries for linear recurrences with constant coefficients, signature (0,0,3,0,0,-3,0,0,1). FORMULA G.f.: -(2*x^7+x^5-4*x^4-x^3+2*x+1) / ((x-1)^3*(x^2+x+1)^3). - Colin Barker, Jul 31 2013 MAPLE a := proc(n) if n mod 3 = 0 then RETURN(n/3+1) fi: if n mod 3 = 1 then RETURN(2) fi: if n mod 3 = 2 then RETURN(((n-2)/3)*((n-2)/3+1)/2) fi: end: for n from 0 to 150 do printf(`%d, `, a(n)) od: MATHEMATICA Flatten[ Table[ {n, 2, n(n - 1)/2}, {n, 1, 27}]] With[{nn=30}, Riffle[Riffle[Range[nn], Accumulate[Range[0, nn]], {2, -1, 2}], 2, {2, -1, 3}]] (* Harvey P. Dale, May 20 2013 *) CROSSREFS Sequence in context: A128664 A003823 A059451 * A286222 A029273 A117963 Adjacent sequences: A083814 A083815 A083816 * A083818 A083819 A083820 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jun 18 2003 EXTENSIONS More terms from James A. Sellers and Robert G. Wilson v, Jun 21 2003 STATUS approved

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Last modified May 30 19:35 EDT 2023. Contains 363055 sequences. (Running on oeis4.)