LINKS
G. C. Greubel, <a href="/A015503/b015503_1.txt">Table of n, a(n) for n = 1..50</a>
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G. C. Greubel, <a href="/A015503/b015503_1.txt">Table of n, a(n) for n = 1..50</a>
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a(1) = 1, a(n) = Sum_{k=1}^{..n-1} ((4^k - 1)/3)*a(k).
[a(n, 54) for n in range(1, 31)] # G. C. Greubel, Apr 29 2023
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a(1) = 1, a(n) = sum_Sum_{k=1}^{k=n-1} ((4^k - 1)/3 )*a(k).
G. C. Greubel, <a href="/A015503/b015503_1.txt">Table of n, a(n) for n = 1..50</a>
a[n_, m_]:= a[n, m]= If[n<3, 1, (m^(n-1)+m-2)*a[n-1, m]/(m-1)];
Table[a[n, 4], {n, 30}] (* G. C. Greubel, Apr 29 2023 *)
(Magma) I:=[1, 1, 6]; [n le 3 2 select I[n] 1 else ((4^(n-1) + 2)/3) * Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012
(SageMath)
@CachedFunction # a = A015503
def a(n, m): return 1 if (n<3) else (m^(n-1) + m-2)*a(n-1, m)/(m-1)
[a(n, 5) for n in range(1, 31)] # G. C. Greubel, Apr 29 2023
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(MAGMAMagma) I:=[1, 1, 6]; [n le 3 select I[n] else ((4^(n-1) + 2)/3) * Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012
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