A143407 Largest number k such that the reduced totient function psi(k) = A002174(n).

2, 24, 240, 504, 480, 264, 65520, 16320, 28728, 13200, 552, 131040, 6960, 171864, 32640, 138181680, 1082400, 151704, 5520, 1128, 4455360, 12720, 86184, 13920, 1416, 6814407600, 65280, 776664, 18744, 20174525280, 39816, 36801600, 1992

Offset: 1

Author

T. D. Noe, Aug 13 2008

Keywords

• nonn

Comments

For each of the values in A002174, there are only a finite number of numbers k such that psi(k)=A002174(n). This sequence gives the largest such k. Sequence A002396 gives the least k. The number of such k is given in A143408. When A002174(n) is twice a Sophie Germain prime, then a(n) is particularly small.

Links

• T. D. Noe, Table of n, a(n) for n=1..1000

Crossrefs

Cf. A002322 (reduced totient function), A002174, A002396, A143408.

Formula

a(n) = A006863(A002174(n)/2) for n>1.