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 A027005 a(n) = T(2*n+1,n+2), T given by A026998. 1
 1, 19, 101, 370, 1148, 3278, 8967, 23993, 63483, 167040, 438346, 1148844, 3009181, 7879855, 20631713, 54016798, 141420392, 370246298, 969320643, 2537718005, 6643835991, 17393792844, 45537545686, 119218847640, 312119000953, 817138159243, 2139295481117 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Bisection of A027963. LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (6,-13,13,-6,1). FORMULA From Colin Barker, Feb 19 2016: (Start) a(n) = (-6+(2^(-1-n)*((3-sqrt(5))^n*(-25+11*sqrt(5)) + (3+sqrt(5))^n*(25+11*sqrt(5))))/sqrt(5) + 7*(1+n) - 6*(1+n)*(2+n)). a(n) = 6*a(n-1)-13*a(n-2)+13*a(n-3)-6*a(n-4)+a(n-5) for n>5. G.f.: x*(1+13*x-2*x^3) / ((1-x)^3*(1-3*x+x^2)). (End) MATHEMATICA LinearRecurrence[{6, -13, 13, -6, 1}, {1, 19, 101, 370, 1148}, 30] (* Harvey P. Dale, Aug 19 2020 *) PROG (PARI) Vec(x*(1+13*x-2*x^3)/((1-x)^3*(1-3*x+x^2)) + O(x^40)) \\ Colin Barker, Feb 19 2016 CROSSREFS Cf. A027963. Sequence in context: A044651 A287303 A142216 * A061696 A062643 A245528 Adjacent sequences: A027002 A027003 A027004 * A027006 A027007 A027008 KEYWORD nonn,easy AUTHOR Clark Kimberling STATUS approved

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Last modified May 20 19:00 EDT 2024. Contains 372720 sequences. (Running on oeis4.)