A063753 Numbers k such that cototient(k) is a square and sets a new record for squares.

2, 6, 21, 24, 54, 96, 189, 216, 345, 384, 420, 796, 864, 1332, 1536, 1680, 2340, 3300, 3780, 5328, 6144, 6516, 6720, 8260, 8484, 9360, 10500, 13200, 14532, 15120, 18340, 19476, 20580, 24576, 26064, 26628, 26880, 29700, 33396, 33936, 34020

Offset: 1

Author

Jason Earls, Aug 11 2001

Keywords

• easy
• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..275

Crossrefs

Cf. A051953.

Programs

PARI

a=0; for(n=1,7000,x=n-eulerphi(n); if(issquare(x),b=x; if(b>a,a=b; print(n))))

PARI

{ n=0; a=0; for (m=1, 10^9, if (issquare(b=m - eulerphi(m)), if (b>a, a=b; write("b063753.txt", n++, " ", m); if (n==275, break))) ) } \\ Harry J. Smith, Aug 29 2009

Extensions

More terms from Dean Hickerson, Aug 22 2001