OFFSET
0,4
COMMENTS
Without the first two 1's: A137531.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..2500
Richard Choulet, Curtz-like transformation.
Index entries for linear recurrences with constant coefficients, signature (3,-2,1).
FORMULA
O.g.f.: f(z) = ((1-z)^2/(1 - 3*z + 2*z^2 - z^3))*(1-z^2).
a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3) for n >= 5, with a(0)=1, a(1)=1, a(2)=1, a(3)=4, a(4)=10.
a(n) = A137531(n-2).
MAPLE
a(0):=1: a(1):=1:a(2):=1: a(3):=4:a(4):=10:for n from 2 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, 1}, LinearRecurrence[{3, -2, 1}, {1, 4, 10}, 50]] (* G. C. Greubel, Jun 16 2018 *)
PROG
(PARI) m=50; v=concat([1, 4, 10], vector(m-3)); for(n=4, m, v[n] = 3*v[n-1] -2*v[n-2] +v[n-3] ); concat([1, 1], v) \\ G. C. Greubel, Jun 16 2018
(Magma) I:=[1, 4, 10]; [1, 1] 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 16 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Richard Choulet, Apr 11 2009
STATUS
approved