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A168097
a(n) = number of natural numbers m such that n - 7 <= m <= n + 7.
0
7, 8, 9, 10, 11, 12, 13, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15
OFFSET
0,1
COMMENTS
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).
FORMULA
a(n) = 7 + n for 0 <= n <= 7, a(n) = 15 for n >= 8.
G.f.: (7 - 6*x - x^9)/(1-x)^2. - G. C. Greubel, Jul 12 2016
MATHEMATICA
CoefficientList[Series[(7 - 6*x - x^9)/(1 - x)^2, {x, 0, 25}], x] (* G. C. Greubel, Jul 12 2016 *)
CROSSREFS
Cf. A000027.
Sequence in context: A006969 A195935 A363783 * A020719 A345435 A162787
KEYWORD
nonn,less
AUTHOR
Jaroslav Krizek, Nov 18 2009
STATUS
approved