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A333827
Least positive integer whose square root starts with at least n odd decimal digits.
2
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
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
KEYWORD
nonn,base
AUTHOR
Jinyuan Wang, Apr 16 2020
EXTENSIONS
Corrected a(31) and more terms from Bert Dobbelaere, Apr 17 2020
STATUS
approved