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A168097 a(n) = number of natural numbers m such that n - 7 <= m <= n + 7. 0

%I

%S 7,8,9,10,11,12,13,14,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,

%T 15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,

%U 15,15,15,15,15,15,15,15

%N a(n) = number of natural numbers m such that n - 7 <= m <= n + 7.

%C Generalization: If a(n,k) = number of natural numbers m such that n - k <= m <= n + k (k >= 1) then a(n,k) = a(n-1,k) + 1 = n + k for 0 <= n <= k, a(n,k) = a(n-1,k) = 2k + 1 for n >= k + 1 (see, e.g., A158799).

%F a(n) = 7 + n for 0 <= n <= 7, a(n) = 15 for n >= 8.

%F G.f.: (7 - 6*x - x^9)/(1-x)^2. - _G. C. Greubel_, Jul 12 2016

%t CoefficientList[Series[(7 - 6*x - x^9)/(1 - x)^2, {x, 0, 25}], x] (* _G. C. Greubel_, Jul 12 2016 *)

%Y Cf. A000027.

%K nonn,less

%O 0,1

%A _Jaroslav Krizek_, Nov 18 2009

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Last modified July 14 09:22 EDT 2020. Contains 335720 sequences. (Running on oeis4.)