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 A323331 Smallest member of sociable quadruples using Dedekind psi function (A001615). 1
 11398670, 22797340, 38369450, 45594680, 56993350, 59334310, 76738900, 91189360, 113986700, 118668620, 153477800, 182378720, 209524210, 227973400, 237337240, 268586150, 284966750, 306955600, 364757440, 419048420, 455946800, 474674480, 537172300, 539867650, 569933500 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k whose iterations of k -> A001615(k) - k are cyclic with a period of 4, and in each cyclic quadruple k is the least of the 4 members. LINKS Table of n, a(n) for n=1..25. EXAMPLE 11398670 is in the sequence since the iterations of k -> A001615(k) - k are cyclic with a period of 4: 11398670, 11475730, 12474350, 14093650, 11398670, ... and 11398670 is the smallest member of the quadruple. MATHEMATICA t[0]=0; t[1]=0; t[n_]:=(Times@@(1+1/Transpose[FactorInteger[n]][[1]])-1)*n; seq[n_]:=NestList [t, n, 4][[2;; 5]] ; aQ[n_] := Module[ {s=seq[n]}, n==Min[s] && Count[s, n]==1]; s={}; Do[If[aQ[n], AppendTo[s, n]], {n, 1, 10^9}]; s CROSSREFS Cf. A001615, A090615, A319902, A319915, A323327, A323328, A323329, A323330. Sequence in context: A069341 A204790 A183826 * A072142 A043674 A141281 Adjacent sequences: A323328 A323329 A323330 * A323332 A323333 A323334 KEYWORD nonn AUTHOR Amiram Eldar, Jan 11 2019 STATUS approved

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Last modified June 20 17:22 EDT 2024. Contains 373530 sequences. (Running on oeis4.)