OFFSET
0,1
COMMENTS
These numbers x also have the property that the Fibonacci sequence starting (1, x, ...) contains the concatenation of 1 and x, but there are other solutions, e.g., x = 14285.
LINKS
R. Israel, in reply to E. Angelini, Fibonacci concatenated, SeqFan list, Jan. 26, 2016
Index entries for linear recurrences with constant coefficients, signature (1,10,-10).
FORMULA
G.f.: (-4/(1 - x) + (2*Sqrt(10))/(1 - Sqrt(10)*x) - 10/(-1 + Sqrt(10)*x) + 10/(1 + Sqrt(10)*x) - (2*Sqrt(10))/(1 + Sqrt(10)*x))/4. - Michael De Vlieger, Jan 26 2016
G.f.: ( 4+5*x ) / ( (x-1)*(10*x^2-1) ). - R. J. Mathar, Mar 12 2017
MATHEMATICA
Table[2^Mod[n, 2]*5*10^Floor[n/2] - 1, {n, 0, 30}] (* or *) LinearRecurrence[{0, 10}, {5, 10}, 30] - 1 (* or *) CoefficientList[Series[(-4/(1 - x) + (2 Sqrt[10])/(1 - Sqrt[10] x) - 10/(-1 + Sqrt[10] x) + 10/(1 + Sqrt[10] x) - (2 Sqrt[10])/(1 + Sqrt[10] x))/4, {x, 0, 30}], x] (* Michael De Vlieger, Jan 26 2016 *)
PROG
(PARI) a(n)=2^bittest(n, 0)*5*10^(n\2)-1
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
M. F. Hasler, Jan 26 2016
STATUS
approved