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 A084241 a(n) = -5*a(n-1)-4*a(n-2) with n>1, a(0)=0, a(1)=1. 2
 0, 1, -5, 21, -85, 341, -1365, 5461, -21845, 87381, -349525, 1398101, -5592405, 22369621, -89478485, 357913941, -1431655765, 5726623061, -22906492245, 91625968981, -366503875925, 1466015503701, -5864062014805, 23456248059221, -93824992236885 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS abs(a(n))=A002450(n)=A001045(2n). Binomial transform is (0,1,-3,9,-27,...). LINKS Index to sequences with linear recurrences with constant coefficients, signature (-5,-4). FORMULA a(n) = ((-1)^n-(-4)^n)/3. a(n) = sum(k=1..n, (-1)^(n+k)*binomial(n, k)(-3)^(k-1)). G.f.: x/((1+x)*(1+4*x)). E.g.f.: (exp(-x)-exp(-4x))/3. MATHEMATICA LinearRecurrence[{-5, -4}, {0, 1}, 40] (* Harvey P. Dale, Dec 20 2014 *) CROSSREFS Apart from signs, identical to A002450. Cf. A084240. Sequence in context: A246986 A247001 A028948 * A002450 A187063 A026855 Adjacent sequences:  A084238 A084239 A084240 * A084242 A084243 A084244 KEYWORD sign,easy,changed AUTHOR Paul Barry, May 21 2003 STATUS approved

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Last modified December 22 22:37 EST 2014. Contains 252372 sequences.