A159742 If an array is made of columns of -nacci sequences (Fibonacci, tribonacci, etc.), all starting with 1,1,2,..., the NW-to-SE diagonals can be extended by computation. This sequence is diagonal 6. See A159741 for details.
13, 44, 108, 236, 492, 1004, 2028, 4076, 8172, 16364, 32748, 65516, 131052, 262124, 524268, 1048556, 2097132, 4194284, 8388588, 16777196, 33554412, 67108844, 134217708, 268435436, 536870892, 1073741804, 2147483628, 4294967276, 8589934572, 17179869164
Offset: 1
Keywords
Links
- G. C. Greubel, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (3,-2).
Programs
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Magma
[13] cat [4*(2^(n+2) - 5): n in [2..30]]; // G. C. Greubel, May 22 2018
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Maple
T := proc(n,m) option remember ; if n < 0 then 0; elif n <= 1 then 1; elif n = 2 then 2; else add(procname(n-i,m),i=1..m) ; fi: end: A159742 := proc(n) T(n+5,n+1) ; end: seq(A159742(n),n=1..40) ; # R. J. Mathar, Apr 22 2009
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Mathematica
CoefficientList[Series[(2*z^2 + 5*z + 13)/(2*z^2 - 3*z + 1), {z, 0, 100}], z] (* Vladimir Joseph Stephan Orlovsky, Jul 08 2011 *) Join[{13}, Table[4*(2^(n + 2) - 5), {n, 2, 50}]] (* G. C. Greubel, May 22 2018 *) LinearRecurrence[{3,-2},{13,44,108},30] (* Harvey P. Dale, Jul 10 2018 *)
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PARI
for(n=1, 30, print1(if(n==1, 13, 4*(2^(n+2) - 5)), ", ")) \\ G. C. Greubel, May 22 2018
Formula
From R. J. Mathar, Apr 22 2009: (Start)
a(n) = 3*a(n-1) - 2*a(n-2), n>3.
a(n) = 16*2^n - 20, n>1. (End)
Extensions
More terms from R. J. Mathar, Apr 22 2009