OFFSET
0,3
COMMENTS
The decimal digits 1, 2, 3, 5, 7 have no hole, and 4 is represented without a hole; otherwise, 0, 6, 9 have one hole each and 8 has two holes.
Least palindrome q such that A064532(q) = n.
Except for a(0) = 1, each term has only digits 0, 6 or 8 in its decimal expansion.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,0,111,0,0,0,-1110,0,0,0,1000).
FORMULA
EXAMPLE
a(3) = 606 because 6 and 0 have each one circular loop for a total of 3.
MATHEMATICA
a[0] = 1; a[n_] := Switch[Mod[n, 4], _?EvenQ, 8*(10^(n/2) - 1)/9, 1, 8*(10^((n + 1)/2) - 9*10^((n - 1)/4) - 1)/9, 3, 8*(10^((n + 3)/2) - 9*10^((n + 1)/4) - 1)/9 - 2*(10^((n + 1)/2) + 1)]; Array[a, 28, 0] (* Amiram Eldar, Sep 26 2020 *)
LinearRecurrence[{0, 0, 0, 111, 0, 0, 0, -1110, 0, 0, 0, 1000}, {1, 0, 8, 606, 88, 808, 888, 68086, 8888, 88088, 88888, 6880886, 888888}, 30] (* Harvey P. Dale, Mar 13 2022 *)
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Bernard Schott, Sep 25 2020
EXTENSIONS
More terms from Amiram Eldar, Sep 25 2020
STATUS
approved