A280578 Integers that are fixed points of some iteration of f(x) = phi(x) + floor(x/2), see A280577.
1, 2, 3, 4, 5, 6, 8, 9, 10, 15, 16, 21, 22, 23, 30, 32, 33, 36, 45, 46, 64, 128, 255, 256, 413, 498, 512, 513, 514, 553, 554, 580, 612, 744, 765, 766, 1024, 1073, 1125, 1162, 1250, 1540, 1544, 2048, 2241, 2413, 2457, 2458, 2522, 2524, 2596, 2754, 2889, 3348, 3352, 3474, 4096
Offset: 1
Keywords
Links
- Michel Marcus, Table of n, a(n) for n = 1..178
- Michel Marcus, Cycles up to 10^7
Programs
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PARI
iscycle(v, nextn) = for (i=1, #v, if (v[i] == nextn, return (1); ); ); return (0); fcycle(n, known) = {v = vector(1); v[1] = n; first = n; while ((nextn = eulerphi(n) + n\2) <= first, if (vecsearch(known, nextn), return([])); if (iscycle(v, nextn), return (v)); v = concat(v, nextn); n = nextn; ); return ([]);} lista(nn) = {known = []; for (n = 1, nn, v = fcycle(n, known); if (#v, known = vecsort(concat(known, v)));); print(known);} \\ corrected by Michel Marcus, Mar 15 2022
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