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

3,1

Links

Table of n, a(n) for n=3..30.

Yasutoshi Kohmoto, UnitaryPhi, SeqFan list, Aug-Sep 2018.

Formula

a(2n) = A318842(n).

Prog

(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; ); }

Crossrefs

Cf. A047994 (unitary totient).

Cf. A030163, A305678, A318842.

Sequence in context: A248269 A081778 A055943 * A277275 A213503 A169632

Adjacent sequences: A319310 A319311 A319312 * A319314 A319315 A319316

Keyword

nonn,more,changed

Author

Michel Marcus, Sep 17 2018

Status

approved