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A171507
a(n) = (5*2^(n+1)-9-(-1)^n)/6-2*n.
2
0, 0, 1, 6, 17, 42, 93, 198, 409, 834, 1685, 3390, 6801, 13626, 27277, 54582, 109193, 218418, 436869, 873774, 1747585, 3495210, 6990461, 13980966, 27961977, 55924002, 111848053, 223696158, 447392369, 894784794, 1789569645, 3579139350, 7158278761, 14316557586
OFFSET
0,4
FORMULA
a(n) = 3*a(n-1)-a(n-2)-3*a(n-3)+2*a(n-4). G.f.: x^2*(1+3*x)/((1+x)*(1-2*x)*(1-x)^2).
a(n) = A084640(n) - A042948(n).
a(n+1)-2*a(n) = A042948(n+1).
First differences: a(n+1)-a(n) = A084640(n).
Last digits: a(n) == a(n+10) (mod 10), n>=1.
MAPLE
A171507:=n->(5*2^(n+1)-9-(-1)^n)/6 -2*n: seq(A171507(n), n=0..50); # Wesley Ivan Hurt, May 03 2017
PROG
(Magma) [(5*2^(n+1)-9-(-1)^n)/6 -2*n: n in [0..40]]; // Vincenzo Librandi, Aug 05 2011
CROSSREFS
Sequence in context: A370589 A343518 A365409 * A099858 A232567 A062020
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Dec 10 2009
EXTENSIONS
Edited and extended by R. J. Mathar, Dec 15 2009
STATUS
approved