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A034491
a(n) = 7^n + 1.
49
2, 8, 50, 344, 2402, 16808, 117650, 823544, 5764802, 40353608, 282475250, 1977326744, 13841287202, 96889010408, 678223072850, 4747561509944, 33232930569602, 232630513987208, 1628413597910450, 11398895185373144
OFFSET
0,1
FORMULA
a(n) = 7*a(n-1) - 6.
a(n) = 8*a(n-1) - 7*a(n-2).
From Mohammad K. Azarian, Jan 02 2009: (Start)
G.f.: 1/(1-x) + 1/(1-7*x).
E.g.f.: exp(x) + exp(7*x). (End)
a(n) = 2*A034494(n). - G. C. Greubel, Mar 11 2023
MATHEMATICA
7^Range[0, 30] +1
LinearRecurrence[{8, -7}, {2, 8}, 20] (* Harvey P. Dale, Aug 18 2018 *)
PROG
(Sage) [sigma(7, n) for n in range(0, 20)] # Zerinvary Lajos, Jun 04 2009
(PARI) a(n)=7^n+1 \\ Charles R Greathouse IV, Sep 24 2015
(Magma) [7^n +1: n in [0..30]]; // G. C. Greubel, Mar 11 2023
KEYWORD
easy,nonn
STATUS
approved