A270265 Numbers that are values of the totient function (A002202) but not of the reduced totient function (A002174).

1936, 3872, 6348, 7744, 9196, 15004, 15488, 18392, 20812, 21160, 22264, 30008, 35332, 36784, 38416, 41624, 42320, 44528, 51304, 58564, 63916, 65596, 70664, 73084, 73568, 76832, 79420, 81796, 82668, 83248, 84100, 84640, 86152, 96040, 102124, 102608, 109384, 110836

Offset: 1

Author

Michel Marcus, Mar 14 2016

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• William D. Banks, John B. Friedlander, Florian Luca, Francesco Pappalardi, and Igor E. Shparlinski, Coincidences in the values of the Euler and Carmichael functions, Acta Arithmetica 122 (2006), 207-234.

Crossrefs

Cf. A000010, A002202.

Cf. A002322, A002174.

Cf. A270266.

Programs

PARI

isA002174(n) = if(n%2, return(n==1)); my(f=factor(n), pe); for(i=1, #f~, if(n%(f[i, 1]-1)==0, next); pe=f[i, 1]^f[i, 2]; forstep(q=2*pe+1, n+1, 2*pe, if(n%(q-1)==0 && isprime(q), next(2))); return(0)); 1 \\ Charles R Greathouse IV at A002174
is(n) = istotient(n) && !isA002174(n); \\ Amiram Eldar, Nov 30 2024

Extensions

More terms from Jinyuan Wang, Feb 13 2020