A319313 a(n) is the least integer m such that A047994(m) = ((n-2)/n)*m where A047994 is the unitary totient function, or 0 if there is no such m.
6, 2, 20, 3, 1008, 4, 72, 5, 4400, 144, 835660800, 7, 10800, 8, 272, 9, 9849600, 400, 208039104, 11, 145520912351232000000, 64281600, 3608344625286776094720000, 13, 1296, 84672, 90944, 129600
Offset: 3
Links
- Yasutoshi Kohmoto, UnitaryPhi, SeqFan list, Aug-Sep 2018.
Programs
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PARI
\\ uses the "solve_uphi pari code", see A318842 links a(n) = {my(lim = 1, v); while (1, v = solve_uphi(n-2, n, lim); if (#v, return (v[1])); lim *= 10; ); }
Formula
a(2n) = A318842(n).