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A195035
Multiples of 15 and of 8 interleaved: a(2n-1) = 15n, a(2n) = 8n.
6
15, 8, 30, 16, 45, 24, 60, 32, 75, 40, 90, 48, 105, 56, 120, 64, 135, 72, 150, 80, 165, 88, 180, 96, 195, 104, 210, 112, 225, 120, 240, 128, 255, 136, 270, 144, 285, 152, 300, 160, 315, 168, 330, 176, 345, 184, 360, 192, 375, 200, 390, 208, 405, 216
OFFSET
1,1
COMMENTS
First differences of A195036.
a(n) is also the length of the n-th edge of a square spiral in which the first two edges are the legs of the primitive Pythagorean triple [15, 8, 17]. Zero together with partial sums give A195036; the vertices of the spiral.
LINKS
FORMULA
From Bruno Berselli, Sep 30 2011: (Start)
G.f.: x*(15+8*x)/((1-x)^2*(1+x)^2).
a(n) = A010686(n)*A010706(n-1)*A004526(n+1) = (23*n-(7*n+15)*(-1)^n+15)/4.
a(n) = 2*a(n-2) - a(n-4).
a(-n) = -a(A014681(n-1)). (End)
MATHEMATICA
Riffle[15*#, 8*#] & [Range[50]] (* Paolo Xausa, Mar 21 2024 *)
PROG
(Magma) &cat[[15*n, 8*n]: n in [1..27]]; // Bruno Berselli, Sep 30 2011
(PARI) a(n)=(n+1)\2*if(n%2, 15, 8) \\ Charles R Greathouse IV, Oct 07 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Sep 12 2011
STATUS
approved