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 A356620 a(n) = number of k-tuples (u(1), u(2), ..., u(k)) with 1 <= u(1) < u(2) < ... < u(k) <= n such that u(i) - u(i-1) <= 4 for i = 2,...,k. 3
 0, 1, 4, 11, 26, 56, 115, 230, 453, 884, 1716, 3321, 6416, 12383, 23886, 46060, 88803, 171194, 330009, 636136, 1226216, 2363633, 4556076, 8782147, 16928162, 32630112, 62896595, 121237118, 233692093, 450456028, 868281948, 1673667305, 3226097496, 6218502903 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..33. Index entries for linear recurrences with constant coefficients, signature (3,-2,0,0,-1,1). FORMULA G.f.: (x (-1 - x - x^2 - x^3))/((-1 + x)^2 (-1 + x + x^2 + x^3 + x^4)). a(n) = 3*a(n-1) - 2*a(n-2) - a(n-5) + a(n-6). MATHEMATICA maxDiff = 4; t = Map[Length[Select[Map[{#, Max[Differences[#]]} &, Drop[Subsets[Range[#]], # + 1]], #[[2]] <= maxDiff &]] &, Range[18]] CROSSREFS Cf. A001891, A356619, A356621. Sequence in context: A290989 A027660 A002940 * A030196 A248425 A356621 Adjacent sequences: A356617 A356618 A356619 * A356621 A356622 A356623 KEYWORD nonn,easy AUTHOR Clark Kimberling, Sep 04 2022 STATUS approved

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Last modified June 15 03:12 EDT 2024. Contains 373402 sequences. (Running on oeis4.)