A131664 A string of n 1's repeated n times.
1, 11, 11, 111, 111, 111, 1111, 1111, 1111, 1111, 11111, 11111, 11111, 11111, 11111, 111111, 111111, 111111, 111111, 111111, 111111, 1111111, 1111111, 1111111, 1111111, 1111111, 1111111, 1111111, 11111111, 11111111, 11111111, 11111111
Offset: 1
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
seq(((10^n-1)/9)$n, n=1..10); # Robert Israel, Jul 08 2019
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Python
from math import isqrt def A131664(n): return (10**(isqrt(n<<3)+1>>1)-1)//9 # Chai Wah Wu, Oct 17 2022
Formula
G.f.: z/(1-z) * Sum_{n>=0} 10^n*z^(n*(n+1)/2).