A164265 Partial sums of A162766.
4, 7, 19, 28, 64, 91, 199, 280, 604, 847, 1819, 2548, 5464, 7651, 16399, 22960, 49204, 68887, 147619, 206668, 442864, 620011, 1328599, 1860040, 3985804, 5580127, 11957419, 16740388, 35872264, 50221171, 107616799, 150663520, 322850404
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (1,3,-3).
Programs
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Magma
T:=[ n le 2 select 5-n else 3*Self(n-2): n in [1..33] ]; [ n eq 1 select T[1] else Self(n-1)+T[n]: n in [1..#T]];
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Mathematica
LinearRecurrence[{1,3,-3},{4,7,19},40] (* Harvey P. Dale, Aug 28 2016 *) -
PARI
a(n)=if(n%2,15,7)*3^(n\2)\2-3 \\ Charles R Greathouse IV, Jul 15 2011
Formula
a(n) = 3*a(n-2)+7 for n > 2; a(1) = 4, a(2) = 7.
a(n) = (11-4*(-1)^n)*3^(1/4*(2*n-1+(-1)^n))/2-7/2.
G.f.: x*(4+3*x)/((1-x)*(1-3*x^2)).