A333827 Least positive integer whose square root starts with at least n odd decimal digits.

1, 1, 3, 3, 63, 91, 91, 249, 249, 384, 391, 391, 2823, 9996, 9996, 17260, 17260, 39984, 39984, 39984, 308642, 308642, 308642, 308642, 308642, 308642, 308642, 308642, 308642, 308642, 99999996, 314558578, 381808465, 381808465, 381808465, 399999984, 399999984, 399999984, 399999984

Offset

0,3

Comments

This sequence is infinite because the square root of 100^k - 1 starts with 2*k odd digits.

Links

Giovanni Resta, Table of n, a(n) for n = 0..59

Example

a(4) = 63 because sqrt(63) = 7.9372539... starts with 4 odd digits.

Prog

(PARI) a(n) = {my(g=10^(n-1), v); for(k=1, oo, if(setintersect([1, 3, 5, 7, 9], v=Set(digits(floor(sqrt(k)*g))[1..n]))==v, return(k))); } \\ Jinyuan Wang, Apr 16 2020

Crossrefs

Cf. A220426.

Sequence in context: A102065 A102074 A126227 * A213137 A260076 A024189

Adjacent sequences: A333824 A333825 A333826 * A333828 A333829 A333830

Keyword

nonn,base

Author

Jinyuan Wang, Apr 16 2020

Extensions

Corrected a(31) and more terms from Bert Dobbelaere, Apr 17 2020

Status

approved