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A141812 RMS values of the RMS numbers: a(n) is the root mean square of the divisors of A140480(n). 8
1, 5, 29, 169, 145, 845, 1105, 2405, 3445, 4901, 2665, 5525, 9425, 12325, 12025, 17225, 24505, 13325, 32045, 55205, 47125, 61625, 69745, 101065, 99905, 77285, 124501, 160225, 186745, 204425, 239425, 160225, 273325, 276025, 292825, 226525, 446165, 456025 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Those numbers seem to be congruent to 0,1,-1 mod 5. - Ctibor O. Zizka, Sep 23 2008

No, the first terms congruent to 2 and 3 mod 5 are a(461) = 247511537 and a(1603) = 7177834573, respectively. - Giovanni Resta, Oct 29 2019

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..7430 (terms 1..455 from Andrew Weimholt, terms 456..1660 from Donovan Johnson)

EXAMPLE

a(5)=145, because A140480(5)=287, with divisors 1,7,41,287 and RMS(1,7,41,287) = 145.

MATHEMATICA

rmsQ[n_] := IntegerQ[Sqrt[DivisorSigma[2, n]/DivisorSigma[0, n]]]; Reap[ For[k=1; n=1, k<10^7, k++, If[rmsQ[k], an = Sqrt[Mean[Divisors[k]^2]]; Print["k = ", k, " a(", n++, ") = ", an]; Sow[an]]]][[2, 1]] (* Jean-Fran├žois Alcover, Dec 04 2015 *)

PROG

(PARI) for(n=1, 1e6, if(issquare(sumdiv(n, d, d^2)/numdiv(n), &s) && denominator(s)==1, print1(s", "))) \\ Charles R Greathouse IV, Mar 08 2013

CROSSREFS

Cf. A140480, A141813, A141814, A141815, A141816.

Sequence in context: A015537 A182017 A291017 * A227206 A001653 A141814

Adjacent sequences:  A141809 A141810 A141811 * A141813 A141814 A141815

KEYWORD

nonn

AUTHOR

Andrew Weimholt, Jul 07 2008

STATUS

approved

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Last modified February 26 11:49 EST 2020. Contains 332279 sequences. (Running on oeis4.)