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A146884
a(n) = 7*Sum_{k=0..n} 6^k.
2
7, 49, 301, 1813, 10885, 65317, 391909, 2351461, 14108773, 84652645, 507915877, 3047495269, 18284971621, 109709829733, 658258978405, 3949553870437, 23697323222629, 142183939335781, 853103636014693, 5118621816088165
OFFSET
0,1
FORMULA
From G. C. Greubel, Oct 12 2022: (Start)
a(n) = (7/5)*(6^(n+1) - 1).
a(n) = 7*A003464(n+1).
a(n) = 7*a(n-1) - 6*a(n-2).
G.f.: 7/((1-x)*(1-6*x)).
E.g.f.: (7/5)*(6*exp(6*x) - exp(x)). (End)
MATHEMATICA
a[n_]:= Sum[7*6^m, {m, 0, n}]; Table[a[n], {n, 0, 30}]
Accumulate[7*6^Range[0, 20]] (* Harvey P. Dale, Dec 18 2021 *)
PROG
(Magma) [n le 2 select 7^n else 7*Self(n-1) -6*Self(n-2): n in [1..31]]; // G. C. Greubel, Oct 12 2022
(SageMath) [(7/5)*(6^(n+1)-1) for n in range(41)] # G. C. Greubel, Oct 12 2022
KEYWORD
nonn,easy,less
AUTHOR
Roger L. Bagula, Nov 02 2008
STATUS
approved