A343739 a(n) is the last digit to appear in sqrt(n) (or -1 if n is a square).

-1, 8, 4, -1, 5, 6, 8, 5, -1, 4, 8, 2, 8, 0, 5, -1, 8, 3, 1, 0, 3, 3, 6, 0, -1, 6, 8, 4, 9, 8, 9, 7, 1, 6, 2, -1, 4, 3, 1, 1, 9, 1, 9, 1, 1, 4, 7, 4, -1, 9, 0, 4, 6, 0, 3, 0, 1, 4, 3, 0, 3, 2, 6, -1, 1, 7, 0, 7, 5, 1, 0, 6, 9, 9, 9, 5, 5, 9, 2, 3, -1, 2, 6, 2

Offset: 1

Author

Jon E. Schoenfield, Jul 05 2021

Keywords

• sign
• base

Comments

For the digit position in sqrt(n) at which the digit a(n) first appears, see A343740.

Examples

			a(2)=8 because 8 is the last digit to appear in sqrt(2) = 1.414213562373095048...;
a(24)=0 because 0 is the last digit to appear in sqrt(24) = 4.898979485566356196394568149411782783931894961313340...
		

Crossrefs

Cf. A023961, A343740, A343741, A343742.

Programs

Mathematica

Table[If[IntegerQ@ Sqrt@ n, -1, Function[s, FirstPosition[#, Max@ #][[1]] - 1 &@ Array[FirstPosition[s, #][[1]] &, 10, 0]]@ RealDigits[Sqrt[n], 10, 120][[1]]], {n, 84}] (* Michael De Vlieger, Jul 06 2021 *)

Formula

a(100^q*n) = a(n), q > 0. - Bernard Schott, Jul 24 2021