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
Keywords
Examples
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).
Links
- Giovanni Resta, Table of n, a(n) for n = 1..200
Programs
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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 *)
Comments