OFFSET
1,1
COMMENTS
a(n) is composed of digits {2,3,6,8}.
FORMULA
EXAMPLE
a(1) = 2 * 10^1 + 8.
a(2) = 23 * 10^2 + 68.
a(3) = 2232 * 10^4 + 6868.
a(4) = 22223323 * 10^8 + 66866868.
a(5) = 2222222233332232 * 10^16 + 6666886866866868.
And
2 = 2 * (10^1 - 1)/9 + 0.
23 = 2 * (10^2 - 1)/9 + 1.
2232 = 2 * (10^4 - 1)/9 + 10.
22223323 = 2 * (10^8 - 1)/9 + 1101.
2222222233332232 = 2 * (10^16 - 1)/9 + 11110010.
And
8 = 8 * (10^1 - 1)/9 - 2 * 0.
68 = 8 * (10^2 - 1)/9 - 2 * 10.
6868 = 8 * (10^4 - 1)/9 - 2 * 1010.
66866868 = 8 * (10^8 - 1)/9 - 2 * 11011010.
6666886866866868 = 8 * (10^16 - 1)/9 - 2 * 1111001011011010.
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 16 2019
STATUS
approved