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A244806 The 180º spoke (or ray) of a hexagonal spiral of Ulam. 7
1, 18, 59, 124, 213, 326, 463, 624, 809, 1018, 1251, 1508, 1789, 2094, 2423, 2776, 3153, 3554, 3979, 4428, 4901, 5398, 5919, 6464, 7033, 7626, 8243, 8884, 9549, 10238, 10951, 11688, 12449, 13234, 14043, 14876, 15733, 16614, 17519, 18448, 19401, 20378, 21379, 22404, 23453, 24526, 25623 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = 12*n^2 - 19*n + 8.

see A056105 example section for its formula.

From Colin Barker, Dec 12 2016: (Start)

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.

G.f.: x*(1 + 15*x + 8*x^2) / (1 - x)^3.

(End)

EXAMPLE

see A056105 example section for its diagram.

MAPLE

A244806:=n->12*n^2 - 19*n + 8: seq(A244806(n), n=1..50); # Wesley Ivan Hurt, Jul 06 2014

MATHEMATICA

f[n_] := 12n^2 - 19n + 8; Array[f, 47]

PROG

(PARI) vector(50, n, 12*n^2 - 19*n + 8) \\ Michel Marcus, Jul 06 2014

(PARI) Vec(x*(1 + 15*x + 8*x^2) / (1 - x)^3 + O(x^50)) \\ Colin Barker, Dec 12 2016

(MAGMA) [12*n^2 - 19*n + 8 : n in [1..50]]; // Wesley Ivan Hurt, Jul 06 2014

CROSSREFS

Cf. A056105, A244802, A056106, A244803, A056107, A244804, A056108, A244805, A056109, A003215, A033577.

Sequence in context: A251252 A155155 A048356 * A027055 A056448 A056438

Adjacent sequences:  A244803 A244804 A244805 * A244807 A244808 A244809

KEYWORD

nonn,easy

AUTHOR

Robert G. Wilson v, Jul 06 2014

STATUS

approved

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Last modified December 13 19:20 EST 2017. Contains 295976 sequences.