OFFSET
1,2
COMMENTS
Candidates for prefixes and suffixes in A090287.
LINKS
Robert Price, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,0,11,0,0,0,-10).
FORMULA
From Colin Barker, Nov 09 2020: (Start)
G.f.: x*(1 + 3*x + 7*x^2 + 9*x^3) / ((1 - x)*(1 + x)*(1 + x^2)*(1 - 10*x^4)).
a(n) = 11*a(n-4) - 10*a(n-8) for n>8.
(End)
MAPLE
a:= n-> [1, 3, 7, 9][1+irem(n-1, 4)]*(10^iquo(n+3, 4)-1)/9:
seq(a(n), n=1..50); # Alois P. Heinz, Nov 09 2020
MATHEMATICA
A338712={}; Do[AppendTo[A338712, FromDigits[ConstantArray[#, i]] & /@{ 1, 3, 7, 9}], {i, 10}]; A338712//Flatten - Robert Price, Sep 21 2023
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
N. J. A. Sloane, Nov 08 2020, following a suggestion from Hugo Pfoertner
STATUS
approved