login
A138119
Concatenation of n digits 1 and 2*n-1 digits 0.
8
10, 11000, 11100000, 11110000000, 11111000000000, 11111100000000000, 11111110000000000000, 11111111000000000000000, 11111111100000000000000000, 11111111110000000000000000000, 11111111111000000000000000000000, 11111111111100000000000000000000000
OFFSET
1,1
COMMENTS
a(n) has 3*n-1 digits.
a(n) is also A147538(n) written in base 2. - Omar E. Pol, Nov 08 2008.
FORMULA
From Colin Barker, Sep 16 2013: (Start)
a(n) = 1100*a(n-1) - 100000*a(n-2).
G.f.: 10*x / ((100*x-1)*(1000*x-1)). (End)
EXAMPLE
n ...... a(n)
1 ....... 10
2 ...... 11000
3 ..... 11100000
4 .... 11110000000
5 ... 11111000000000
MATHEMATICA
LinearRecurrence[{1100, -100000}, {10, 11000}, 15] (* Paolo Xausa, Feb 06 2024 *)
PROG
(PARI) Vec(10*x/((100*x-1)*(1000*x-1)) + O(x^100)) \\ Colin Barker, Sep 16 2013
KEYWORD
base,easy,nonn
AUTHOR
Omar E. Pol, Apr 03 2008
STATUS
approved