OFFSET
1,1
COMMENTS
n cannot end in the decimal digits 4, 5 or 6; but it most often ends in 0 since if n is present so is 10*n.
n cannot start with the decimal digits 5 or 8. It usually starts with either 3 or 1.
n must lie between 1*10^k & sqrt(2)*10^k, 2*10^k & sqrt(5)*10^k, 3 & sqrt(12)*10^k, sqrt(14)*10^k & sqrt(15)*10^k, sqrt(19)*10^k & sqrt(20)*10^k, sqrt(40)*10^k & sqrt(45)*10^k, sqrt(49)*10^k & sqrt(50)*10^k, sqrt(90)*10^k & sqrt(92)*10^k, sqrt(94)*10^k & sqrt(95)*10^k, sqrt(99)*10^k & sqrt(100)*10^k; for k>0.
EXAMPLE
138 = 19044 which has only the decimal digits 0, 1, 4 & 9. Therefore it is in the sequence.
MATHEMATICA
fQ[n_] := Union[IntegerDigits[n^2]] == {0, 1, 4, 9}; Select[ Range@ 65000, fQ]
PROG
(PARI) isok(n) = Set(digits(n^2)) == [0, 1, 4, 9]; \\ Michel Marcus, Aug 01 2018
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Jul 31 2018
STATUS
approved