A141391 a(n) is the smallest unused number such that the RMS (Root Mean Square) of a(1) through a(n) is an integer.

1, 7, 5, 11, 28, 14, 182, 70, 2, 66, 1518, 462, 1540, 616, 296, 600, 1950, 750, 10, 730, 2336, 876, 2436, 996, 3154, 1162, 5698, 210, 1554, 3234, 1638, 5382, 1872, 23088, 4368, 5934, 201, 4359, 77991, 7021, 13090, 4270, 12950, 74, 12802, 76466, 16954

Offset

1,2

Comments

Actual RMS values are given by A141392

Links

Giovanni Resta, Table of n, a(n) for n = 1..200

Example

a(4) = 11. Sqrt(mean(1^2, 7^2, 5^2, k^2)) is an integer for k in {5,11,37}. We have already used 5 for a(3), so 11 is the smallest value available for a(4).

Mathematica

s={1}; Do[i=1; Until[!MemberQ[s, i]&&IntegerQ[RootMeanSquare[Append[s, i]]], i++]; AppendTo[s, i], {n, 46}]; s (* James C. McMahon, Jul 24 2025 *)

Crossrefs

Cf. A141392, A141393, A141394, A140480.

Sequence in context: A305042 A247870 A367689 * A135766 A067745 A369797

Adjacent sequences: A141388 A141389 A141390 * A141392 A141393 A141394

Keyword

nonn

Author

Andrew Weimholt, Jun 29 2008

Status

approved