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 A139814 a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4); a(0)=0,a(1)=1,a(2)=3,a(3)=7. 1
 0, 1, 3, 7, 11, 23, 47, 95, 187, 375, 751, 1503, 3003, 6007, 12015, 24031, 48059, 96119, 192239, 384479, 768955, 1537911, 3075823, 6151647, 12303291, 24606583, 49213167, 98426335, 196852667, 393705335, 787410671, 1574821343, 3149642683 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Index to sequences with linear recurrences with constant coefficients, signature (1,1,1,2). FORMULA O.g.f.: -x(1+2x+3x^2)/((2x-1)(1+x)(x^2+1)). a(n) = (-1)^(n+1)/3 +11*2^n/15 -2*(-1)^[n/2]*A000034(n)/5 . - R. J. Mathar, May 24 2008 a(n)=(2/5+1/5*I)*I^n+(1/3)*(-1)^n+(11/30)*2^n+(2/5-1/5*I)*(-I)^n, with n>=1 and I=(-1)^(1/2) - Paolo P. Lava, Jun 03 2008 MATHEMATICA LinearRecurrence[{1, 1, 1, 2}, {0, 1, 3, 7}, 35]  (* From Harvey P. Dale, Apr 20 2011 *) CROSSREFS Cf. A132429. Sequence in context: A139253 A116606 A188132 * A099902 A092284 A024459 Adjacent sequences:  A139811 A139812 A139813 * A139815 A139816 A139817 KEYWORD nonn,easy AUTHOR Paul Curtz, May 23 2008 EXTENSIONS More terms from R. J. Mathar, May 24 2008 STATUS approved

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