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A070260 Third diagonal of triangle defined in A051537. 3
3, 2, 15, 6, 35, 12, 63, 20, 99, 30, 143, 42, 195, 56, 255, 72, 323, 90, 399, 110, 483, 132, 575, 156, 675, 182, 783, 210, 899, 240, 1023, 272, 1155, 306, 1295, 342, 1443, 380, 1599, 420, 1763, 462, 1935, 506, 2115, 552, 2303, 600, 2499, 650, 2703, 702 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0,3,0,-3,0,1).

FORMULA

From Vladeta Jovovic, May 09 2002: (Start)

a(n) = n*(n+2)/4 if n is even else n*(n+2).

a(n) = 3*a(n-2) - 3*a(n-4) + a(n-6).

G.f.: x*(3 + 2*x + 6*x^2 - x^4)/(1 - x^2)^3.

(End)

E.g.f.: (x/4)*((12 + x)*cosh(x) + (3 + 4*x)*sinh(x)). - G. C. Greubel, Jul 20 2017

MATHEMATICA

Table[ LCM[i + 2, i] / GCD[i + 2, i], {i, 1, 60}]

PROG

(PARI) Vec(x*(3+2*x+6*x^2-x^4) / (1-x^2)^3 + O(x^60)) \\ Colin Barker, Mar 27 2017

CROSSREFS

Bisections: A002378, A000466.

Sequence in context: A086485 A068310 A033314 * A142705 A072346 A103236

Adjacent sequences:  A070257 A070258 A070259 * A070261 A070262 A070263

KEYWORD

nonn,easy

AUTHOR

Amarnath Murthy, May 09 2002

EXTENSIONS

More terms from Vladeta Jovovic, May 09 2002

STATUS

approved

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Last modified August 19 18:51 EDT 2019. Contains 326133 sequences. (Running on oeis4.)