A379268 Numbers with only digits "1" and two digits "0".
100, 1001, 1010, 1100, 10011, 10101, 10110, 11001, 11010, 11100, 100111, 101011, 101101, 101110, 110011, 110101, 110110, 111001, 111010, 111100, 1001111, 1010111, 1011011, 1011101, 1011110, 1100111, 1101011, 1101101, 1101110, 1110011, 1110101, 1110110, 1111001
Offset: 1
Programs
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Mathematica
Select[Range[10^7],Count[IntegerDigits[#],0]==2&&Max[IntegerDigits[#]]==1&] (* James C. McMahon, Dec 20 2024 *)
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Python
from math import isqrt, comb from sympy import integer_nthroot def A379268(n): a = (m:=integer_nthroot(6*n, 3)[0])+(n>comb(m+2,3))+2 b = isqrt((j:=comb(a,3)-n+1)<<3)+1>>1 c = j-comb((r:=isqrt(w:=j<<1))+(w>r*(r+1)),2)-1 return (10**a-1)//9-10**b-10**c
Comments