A318842 a(n) is the least integer m such that A047994(m) = ((n-1)/n)*m where A047994 is the unitary totient function, or 0 if there is no such m.
2, 3, 4, 5, 144, 7, 8, 9, 400, 11, 64281600, 13, 84672, 129600, 16, 17, 518400, 19, 4327213363200, 254016, 6326996189184000000, 23, 300174920860041216000, 25, 2747437056, 27, 3136, 29
Offset: 2
Links
- Yasutoshi Kohmoto, UnitaryPhi, SeqFan list, Aug 31 2018.
- Michel Marcus, solve_uphi pari code
Crossrefs
Programs
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PARI
\\ uses the "solve_uphi pari code", see links a(n) = {my(lim = 1, v); while (1, v = solve_uphi(n-1, n, lim); if (#v, return (v[1])); lim *= 10;);}
Formula
a(pp) = pp iff pp is a prime power (A000961) > 1.
Comments