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%I #17 Sep 08 2022 08:45:57
%S 1,3,7,23,73,240,819,2849,10082,36157,131071,479349,1766022,6547206,
%T 24403223,91382282,343597383,1296593900,4908534052,18635790301,
%U 70936234050,270649016067,1034834473200,3964436291699,15214863605981,58488306848967,225179981368524
%N a(n) = floor((-1 + 4^n)/(-1 + 3*n)).
%H Vincenzo Librandi, <a href="/A191638/b191638.txt">Table of n, a(n) for n = 1..1000</a>
%t f[n_] := Floor[(-1+4^n)/(-1+3 n)]
%t Table[f[n], {n, 1, 40}] (* A191638 *)
%o (Magma) [Floor((-1+4^n)/(-1+3*n)): n in [1..30] ];// _Vincenzo Librandi_, Sep 10 2011
%o (Maxima) A191638(n):=floor((-1+4^n)/(-1+3*n))$ makelist(A191638(n),n,1,30); /* _Martin Ettl_, Oct 25 2012 */
%Y Cf. A191639.
%K nonn
%O 1,2
%A _Clark Kimberling_, Jun 09 2011
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