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A362969
Nonunitary near-perfect numbers: k such that nusigma(k) = k + d where d is a nonunitary divisor of k.
1
48, 80, 96, 160, 224, 352, 416, 480, 896, 1472, 1476, 1856, 2688, 3968, 6016, 7552, 7808, 8550, 8700, 10332, 17010, 20300, 22496, 36448, 44384, 54944, 63488, 65024, 71264, 73710, 97300, 97792, 114176, 122368, 128512, 310976, 392192, 490496, 515072, 521216, 549990
OFFSET
1,1
COMMENTS
The nonunitary version of near-perfect numbers (A181595).
LINKS
EXAMPLE
For k = 352, nusigma(352) = 360. 360 - 352 = 8, which is a nonunitary divisor of 352.
MATHEMATICA
q[n_] := Module[{d = Select[Divisors[n], ! CoprimeQ[#, n/#] &], s}, s = Total[d]; AnyTrue[d, n + # == s &]]; Select[Range[10^4], q] (* Amiram Eldar, May 11 2023 *)
PROG
(PARI) nusigma(n) = {my(f = factor(n)); sigma(f) - prod(i = 1, #f~, f[i, 1]^f[i, 2] + 1); }
is(n) = {my(d = nusigma(n) - n); d > 0 && !(n%d) && gcd(d, n/d) > 1; } \\ Amiram Eldar, May 20 2023
CROSSREFS
Cf. A048146 (nusigma), A181595.
Sequence in context: A335281 A335196 A348527 * A110229 A108608 A030628
KEYWORD
nonn
AUTHOR
Jenaro Tomaszewski, May 10 2023
STATUS
approved