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A037569
Base 4 digits are, in order, the first n terms of the periodic sequence with initial period 2,1,2.
1
2, 9, 38, 154, 617, 2470, 9882, 39529, 158118, 632474, 2529897, 10119590, 40478362, 161913449, 647653798, 2590615194, 10362460777, 41449843110, 165799372442, 663197489769, 2652789959078, 10611159836314, 42444639345257
OFFSET
1,1
FORMULA
G.f.: x*(2+x+2*x^2) / ((x-1)*(4*x-1)*(1+x+x^2)). - R. J. Mathar, Nov 21 2011
a(n) = 4*(n-1) + a(n-3) - 4*a(n-4). - Vincenzo Librandi, Jun 17 2012
MATHEMATICA
With[{c=PadRight[{}, 30, {2, 1, 2}]}, Table[FromDigits[Take[c, n], 4], {n, 30}]] (* Harvey P. Dale, Nov 06 2011 *)
LinearRecurrence[{4, 0, 1, -4}, {2, 9, 38, 154}, 40] (* Vincenzo Librandi, Jun 17 2012 *)
PROG
(Magma) I:=[2, 9, 38, 154]; [n le 4 select I[n] else 4*Self(n-1)+Self(n-3)-4*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jun 17 2012
CROSSREFS
Sequence in context: A181339 A291265 A037489 * A291462 A001077 A150993
KEYWORD
nonn,base
STATUS
approved