A292048 Squarefree numbers n such that psi(phi(n)) = phi(psi(n) - n).

2, 30, 35070, 36570, 43230, 159810, 224610, 331170, 525630, 1039890, 1094730, 1290810, 1656930, 1770510, 2139990, 4878390, 5110710, 5996310, 6052530, 6127890, 7493430, 9918930, 10146570, 12171810, 12551370, 13821870, 21398370, 23282130, 25587030, 30223830, 31317510, 31364970

Offset

1,1

Links

Table of n, a(n) for n=1..32.

Example

30 = 2*3*5 is a term because psi(phi(30)) = phi(psi(30)-30).
60 = 30*2 is not a term because it is not a squarefree number.

Prog

(PARI) a001615(n) = my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1));
isok(n) = issquarefree(n) && a001615(eulerphi(n))==eulerphi(a001615(n)-n); \\ after Charles R Greathouse IV at A001615

Crossrefs

Cf. A000010, A001615, A290002.

Sequence in context: A371205 A090600 A113511 * A062008 A091776 A159578

Adjacent sequences: A292045 A292046 A292047 * A292049 A292050 A292051

Keyword

nonn

Author

Altug Alkan, Sep 08 2017

Status

approved