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A343216 Numbers k such that A003415(sigma(k)) < k. 6
1, 2, 4, 9, 13, 16, 18, 25, 36, 37, 49, 50, 61, 64, 73, 81, 97, 100, 101, 109, 113, 121, 137, 144, 157, 169, 173, 181, 193, 225, 229, 241, 242, 256, 257, 277, 281, 289, 313, 317, 324, 325, 333, 337, 353, 361, 373, 397, 400, 401, 409, 421, 433, 441, 457, 484, 512, 529, 541, 549, 576, 577, 578, 601, 613, 617, 625, 641 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MATHEMATICA
Select[Range[641], If[#2 < 2, 0, #2 Total[#2/#1 & @@@ FactorInteger[#2]]] < #1 & @@ {#, DivisorSigma[1, #]} &] (* Michael De Vlieger, Apr 08 2021 *)
PROG
(PARI)
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
isA343216(n) = (A003415(sigma(n))<n);
CROSSREFS
Cf. A343217 (complement).
Sequence in context: A129376 A266582 A227759 * A320514 A210640 A024925
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 08 2021
STATUS
approved

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Last modified March 28 07:33 EDT 2024. Contains 371235 sequences. (Running on oeis4.)