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 A240597 Numbers k such that sigma(k) == k (mod 9). 1
 1, 15, 24, 42, 60, 64, 69, 78, 90, 100, 114, 123, 133, 147, 153, 177, 186, 198, 222, 231, 240, 258, 259, 270, 276, 288, 289, 306, 339, 360, 366, 393, 402, 403, 414, 429, 438, 447, 459, 474, 477, 492, 495, 501, 507, 511, 522, 582, 588, 594, 600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS That is, numbers k that satisfy the following: A010878(k) = A105852(k) or A010878(k) = A010878(A000203(k)). A010888(k) = A190998(k) or A010888(k) = A010888(A000203(k)). LINKS Ivan N. Ianakiev, Table of n, a(n) for n = 1..10000 FORMULA A010888(a(n)) = A010888(A000203(a(n))). A010888(a(n)) = A190998(a(n)). EXAMPLE sigma(15) = 24. 24 == 15 (mod 9), therefore 15 is in the sequence. MATHEMATICA Select[Range[1000], Mod[#, 9]==Mod[DivisorSigma[1, #], 9]&] CROSSREFS Cf. A000203, A190998, A010878, A105852, A010888. Sequence in context: A079721 A089952 A295160 * A162964 A067343 A247315 Adjacent sequences:  A240594 A240595 A240596 * A240598 A240599 A240600 KEYWORD easy,nonn AUTHOR Ivan N. Ianakiev, Sep 13 2014 STATUS approved

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Last modified May 25 19:19 EDT 2022. Contains 354071 sequences. (Running on oeis4.)