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 A140498 a(n) = 3*a(n-1)-3*a(n-2)+3*a(n-3) with a(0)=1, a(1)=3, a(2)=7. 0
 1, 3, 7, 15, 33, 75, 171, 387, 873, 1971, 4455, 10071, 22761, 51435, 116235, 262683, 593649, 1341603, 3031911, 6851871, 15484689, 34994187, 79084107, 178723827, 403901721, 912786003, 2062824327, 4661820135, 10535345433, 23809048875, 53806570731, 121598601867 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Second differences of A137256. LINKS Index to sequences with linear recurrences with constant coefficients, signature (3,-3,3). FORMULA G.f.: (1+x^2)/(1-3*x+3*x^2-3*x^3). - Colin Barker, Mar 28 2012 PROG (MAGMA) m:=32; R:=PowerSeriesRing(Integers(), m); Coefficients(R!((1+x^2)/(1-3*x+3*x^2-3*x^3))); // Bruno Berselli, Mar 28 2012 CROSSREFS Sequence in context: A146654 A193641 A026701 * A136029 A225338 A101892 Adjacent sequences:  A140495 A140496 A140497 * A140499 A140500 A140501 KEYWORD nonn,easy AUTHOR Paul Curtz, Jun 29 2008 EXTENSIONS More terms from Colin Barker, Mar 28 2012 STATUS approved

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