A181660 Numbers at which the sum of the iterated totient function (A092693) attains a minimum.

1, 2, 6, 12, 18, 30, 42, 54, 60, 66, 90, 126, 150, 210, 270, 294, 330, 420, 462, 630, 660, 840, 882, 1050, 1260, 1470, 1680, 1890, 2310, 2730, 2940, 3150, 3234, 3570, 3990, 4410, 4620, 4830, 5250, 5460, 5670, 6090, 6930, 7350, 8190, 9030, 9240, 9450, 9660

Offset

1,2

Comments

That is, for each n in this sequence, A092693(n) < A092693(m) for m > n. Do all primorials appear here?

Links

T. D. Noe, Table of n, a(n) for n=1..300

Mathematica

kMax=2*3*5*7*11*13; t=Table[0, {kMax}]; Do[e=EulerPhi[k]; t[[k]]=e+t[[e]], {k, 2, kMax}]; mn=Infinity; Reverse[Reap[Do[If[t[[ -k]]<mn, mn=t[[ -k]]; Sow[kMax-k+1]], {k, kMax}]][[2, 1]]]

Crossrefs

Cf. A181659

Sequence in context: A006511 A325708 A113274 * A036913 A317089 A117311

Adjacent sequences: A181657 A181658 A181659 * A181661 A181662 A181663

Keyword

nonn

Author

T. D. Noe, Nov 04 2010

Status

approved