OFFSET
0,2
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).
FORMULA
n*(10*n-3), if n >= 1, and (2*n+1)*(5*n+1)-1, if n >= 0, interleaved.
G.f.: x*(7+3*x)/((1+x)*(1-x)^3). - Bruno Berselli, Oct 14 2011
MATHEMATICA
LinearRecurrence[{2, 0, -2, 1}, {0, 7, 17, 34}, 50] (* Paolo Xausa, Feb 09 2024 *)
PROG
(Magma) &cat[[n*t, (n+1)*t] where t is 10*n+7: n in [0..22]]; // Bruno Berselli, Oct 14 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Sep 26 2011
EXTENSIONS
Concise definition by Bruno Berselli, Oct 14 2011
STATUS
approved