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 A015841 Numbers k such that phi(k) | sigma(k+4). 6
 1, 2, 3, 6, 7, 8, 10, 17, 18, 24, 26, 42, 50, 52, 54, 56, 65, 75, 80, 81, 87, 90, 110, 111, 114, 120, 126, 154, 164, 186, 216, 234, 244, 245, 306, 308, 338, 344, 350, 351, 371, 372, 374, 416, 436, 456, 490, 528, 560, 570, 598, 626, 682, 689, 759, 777, 836, 866 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Ivan Neretin, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Range[3000], Divisible[DivisorSigma[1, 4 + #], EulerPhi[#]] &] (* David Nacin, Mar 03 2012 *) PROG (PARI) isok(n) = !(sigma(n+4) % eulerphi(n)); \\ Michel Marcus, Feb 05 2017 CROSSREFS Sequence in context: A072685 A119960 A273265 * A175893 A031470 A047223 Adjacent sequences:  A015838 A015839 A015840 * A015842 A015843 A015844 KEYWORD nonn AUTHOR EXTENSIONS a(1) = 1 inserted by Ivan Neretin, Feb 05 2017 STATUS approved

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Last modified January 24 19:03 EST 2022. Contains 350565 sequences. (Running on oeis4.)