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A159337
Transform of the finite sequence (1, 0, -1, 0, 1) by the T_{1,0} transformation (see link).
3
1, 2, 4, 11, 27, 61, 141, 328, 763, 1774, 4124, 9587, 22287, 51811, 120446, 280003, 650928, 1513224, 3517819, 8177937, 19011397, 44196136, 102743551, 238849778, 555258368, 1290819099, 3000790339, 6975991187, 16217211982, 37700443911
OFFSET
0,2
FORMULA
O.g.f.: f(z) = ((1-z)^2/(1-3*z+2*z^2-z^3))*(1-z^2+z^4)+(z/(1-3*z+2*z^2-z^3)).
a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3) for n >= 7, with a(0)=1, a(1)=2,a(2)=4, a(3)=11, a(4)=27, a(5)=61, a(6)=141.
MAPLE
a(0):=1: a(1):=2:a(2):=4: a(3):=11:a(4):=27:a(5):=61:a(6):=141:for n from 4 to 31 do a(n+3):=3*a(n+2)-2*a(n+1)+a(n):od:seq(a(i), i=0..31);
MATHEMATICA
Join[{1, 2, 4, 11}, LinearRecurrence[{3, -2, 1}, {27, 61, 141}, 997]] (* G. C. Greubel, Jun 25 2018 *)
PROG
(PARI) z='z+O('z^50); Vec(((1-z)^2/(1-3*z+2*z^2-z^3))*(1-z^2+z^4)+(z/(1-3*z+2*z^2-z^3))) \\ G. C. Greubel, Jun 25 2018
(Magma) I:=[27, 61, 141]; [1, 2, 4, 11] cat [n le 3 select I[n] else 3*Self(n-1) - 2*Self(n-2) + Self(n-3): n in [1..50]]; // G. C. Greubel, Jun 25 2018
CROSSREFS
Cf. A159336.
Sequence in context: A090899 A159338 A159339 * A243736 A316772 A123440
KEYWORD
easy,nonn
AUTHOR
Richard Choulet, Apr 11 2009
STATUS
approved