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A289873 Related to perfect Wichmann rulers: a(n) = ( n^2 - (mod(n, 6) - 3)^2 ) / 3. 3
1, 3, 5, 7, 9, 15, 21, 27, 33, 39, 45, 55, 65, 75, 85, 95, 105, 119, 133, 147, 161, 175, 189, 207, 225, 243, 261, 279, 297, 319, 341, 363, 385, 407, 429, 455, 481, 507, 533, 559, 585, 615, 645, 675, 705, 735, 765, 799, 833, 867, 901, 935, 969, 1007, 1045, 1083, 1121, 1159, 1197, 1239, 1281, 1323, 1365 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Leading term in length A289761 of longest perfect Wichmann ruler with n segments.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 2..10001

FORMULA

a(n) = A289761(n) - n.

G.f.: x^2*(1 + x - x^2)*(1 + x^2 - x^3 + 2*x^4 + x^5) / ((1 - x)^3*(1 + x)*(1 - x + x^2)*(1 + x + x^2)) (conjectured). - Colin Barker, Jul 14 2017

Can be seen as a family of parabolas p_{n}(x) = (2*n - 3*(1 + x))*(1 + x) evaluated at x = 2*floor(n/6)). - Peter Luschny, Jul 14 2017

MAPLE

p := (n, x) -> (2*n - 3*(1 + x))*(1 + x):

a := n -> p(n, 2*floor(n/6)):

seq(a(n), n = 2..64); # Peter Luschny, Jul 14 2017

MATHEMATICA

Table[(n^2 - (Mod[n, 6] - 3)^2)/3, {n, 2, 64}] (* Michael De Vlieger, Jul 14 2017 *)

CROSSREFS

Cf. A004137, A193802, A193803, A289761.

A014641 is a subsequence.

Sequence in context: A211119 A211123 A290514 * A018736 A211134 A211132

Adjacent sequences:  A289870 A289871 A289872 * A289874 A289875 A289876

KEYWORD

nonn,easy

AUTHOR

Hugo Pfoertner, Jul 14 2017

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)