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A174474
a(n) = (2*n^2 - 2*n - 3)/8 + 3*(-1)^n*(1-2*n)/8.
3
0, 0, -1, 3, 0, 8, 3, 15, 8, 24, 15, 35, 24, 48, 35, 63, 48, 80, 63, 99, 80, 120, 99, 143, 120, 168, 143, 195, 168, 224, 195, 255, 224, 288, 255, 323, 288, 360, 323, 399, 360, 440, 399, 483, 440, 528, 483, 575, 528, 624, 575
OFFSET
0,4
COMMENTS
First differences are (-1)^n*A022998(n).
FORMULA
Bisections: a(2n) = A067998(n). a(2n+1) = A005563(n).
a(2n) + a(2n+1) = A001105(n).
a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) - a(n-4) + a(n-5).
G.f.: x^2*(1 - 4*x + x^2) / ( (1+x)^2*(x-1)^3 ).
MATHEMATICA
LinearRecurrence[{1, 2, -2, -1, 1}, {0, 0, -1, 3, 0}, 60] (* Harvey P. Dale, Jun 01 2015 *)
PROG
(Magma) [(2*n^2-2*n-3)/8+3*(-1)^n*(1-2*n)/8: n in [0..60]]; // Vincenzo Librandi, Aug 04 2011
CROSSREFS
Sequence in context: A372827 A180661 A363053 * A317300 A007391 A247668
KEYWORD
sign,easy
AUTHOR
Paul Curtz, Nov 28 2010
STATUS
approved