1,1

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.

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

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

Cf. A002322 (reduced totient function).

Sequence in context: A121213 A147538 A025131 this_sequence A132596 A099669 A019520

Adjacent sequences: A143404 A143405 A143406 this_sequence A143408 A143409 A143410

nonn

T. D. Noe (noe(AT)sspectra.com), Aug 13 2008