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A347881 Odd numbers k for which A003415(sigma(k^2)) > k^2, where A003415 is the arithmetic derivative. 3
105, 201, 231, 237, 259, 273, 315, 333, 399, 429, 455, 469, 483, 525, 553, 555, 585, 603, 627, 651, 665, 693, 711, 741, 763, 777, 819, 855, 871, 903, 975, 1001, 1005, 1027, 1057, 1071, 1085, 1113, 1119, 1141, 1155, 1185, 1197, 1209, 1221, 1235, 1273, 1281, 1287, 1295, 1351, 1365, 1395, 1407, 1443, 1449, 1463, 1467, 1501 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Odd numbers k such that A342926(k^2) is strictly positive.

Square roots of odd squares present in A343218.

LINKS

Table of n, a(n) for n=1..59.

MATHEMATICA

ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[1, 1501, 2], ad[DivisorSigma[1, #^2]] > #^2 &] (* Amiram Eldar, Sep 18 2021 *)

PROG

(PARI)

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

isA347881(n) = ((n%2)&&(A003415(sigma(n^2))>(n^2)));

CROSSREFS

Cf. A000203, A003415, A343218, A342926, A347882 (subsequence).

Sequence in context: A026066 A167629 A326141 * A044337 A044718 A239827

Adjacent sequences:  A347878 A347879 A347880 * A347882 A347883 A347884

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 18 2021

STATUS

approved

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Last modified August 17 12:09 EDT 2022. Contains 356189 sequences. (Running on oeis4.)