A333132 a(n) = n for n <= 3; thereafter a(n) = 2^(a(n-1)-1) + a(n-1).
1, 2, 3, 7, 71, 1180591620717411303495
Offset: 1
Keywords
Examples
a(5) = 71, 71 in base 2 (reverse order of digits) = 1110001. ||| | 123 7
Programs
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Mathematica
a[n_] := a[n] = If[n <= 3, n, 2^(a[n - 1] - 1) + a[n - 1]]; Table[a[n], {n, 1, 6}]
Formula
a(n) = n for n <= 2; thereafter a(n) = Sum_{k=1..n-1} 2^(a(k)-1).
Comments