OFFSET
1,2
REFERENCES
Maarten Looijen, Over getallen gesproken - Talking about numbers, Van Haren Publishing, 2018, page 513.
LINKS
Giovanni Resta, Zygodrome.
Index entries for linear recurrences with constant coefficients, signature (2,8,-9).
FORMULA
a(n) = A015445(n) - 1.
From Stefano Spezia, Sep 07 2024: (Start)
G.f.: 9*x^2/((1 - x)*(1 - x - 9*x^2)).
E.g.f.: exp(x/2)*(cosh(sqrt(37)*x/2) + sinh(sqrt(37)*x/2)/sqrt(37)) - exp(x). (End)
MATHEMATICA
LinearRecurrence[{1, 9}, {1, 10}, 26] - 1 (* Amiram Eldar, Sep 06 2024 *)
PROG
(PARI) a(n) = ([0, 1; 9, 1]^n)[2, 2] - 1;
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Ruud H.G. van Tol, Sep 06 2024
STATUS
approved