The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A123011 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A123011

a(n) = 2*a(n-1) + 5*a(n-2) for n > 1; a(0) = 1, a(1) = 5.
(history; published version)

#19 by Hugo Pfoertner at Sun Sep 15 13:43:03 EDT 2024

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reviewed

approved

#18 by Michel Marcus at Sun Sep 15 12:47:08 EDT 2024

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proposed

reviewed

#17 by Robert C. Lyons at Sun Sep 15 11:34:43 EDT 2024

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editing

proposed

#16 by Robert C. Lyons at Sun Sep 15 11:34:41 EDT 2024

PROG

(Magma) [ n le 2 select 4*n-3 else 2*Self(n-1)+5*Self(n-2): n in [1..24] ]; - _// _Klaus Brockhaus_, Aug 15 2009

STATUS

approved

editing

#15 by Charles R Greathouse IV at Thu Sep 08 08:45:28 EDT 2022

PROG

(MAGMAMagma) [ n le 2 select 4*n-3 else 2*Self(n-1)+5*Self(n-2): n in [1..24] ]; - Klaus Brockhaus, Aug 15 2009

Discussion

Thu Sep 08

08:45

OEIS Server: https://oeis.org/edit/global/2944

#14 by Michel Marcus at Wed Jul 14 03:22:03 EDT 2021

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reviewed

approved

#13 by Joerg Arndt at Wed Jul 14 03:07:03 EDT 2021

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proposed

reviewed

#12 by Joerg Arndt at Wed Jul 14 03:06:50 EDT 2021

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editing

proposed

#11 by Joerg Arndt at Wed Jul 14 03:06:45 EDT 2021

COMMENTS

a(n) is also 5^(n-1) times the sum of the two elements in the top row of the n-th power of the symmetric matrix (0,1; 1/5,2/5). - see Mathematica code.

MATHEMATICA

M:= {{0, 5}, {1, 2}}; v[1]= {1, 1}; v[n_]:= v[n]= M.v[n-1];

Table[v[n][[1]], {n, 1, 30}]

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proposed

editing

#10 by G. C. Greubel at Wed Jul 14 03:04:11 EDT 2021

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editing

proposed