A056996 Positive integers not of the form sigma(k) + phi(k) - 2k for some k.

5, 11, 19, 21, 23, 27, 33, 35, 39, 43, 45, 47, 51, 53, 55, 59, 67, 69, 71, 79, 81, 83, 87, 95, 99, 101, 103, 105, 107, 113, 115, 117, 119, 123, 129, 131, 135, 139, 141, 143, 147, 151, 153, 155, 159, 165, 167, 171, 173, 175, 177, 179, 185, 187, 189, 191, 193, 195

Offset: 1

Author

David W. Wilson, Sep 06 2000

Keywords

• nonn

Comments

Under the assumption that every even integer >= 18 is the sum of three distinct primes, all elements of this sequence are odd. See A278373 for more details.

Links

• David W. Wilson, Table of n, a(n) for n = 1..10000

Crossrefs

Complement is A278373.

Cf. A000010 (phi), A000203 (sigma).

Programs

Mathematica

Take[#, 59] &@ Complement[Range@ #, Union@ Table[DivisorSigma[1, n] + EulerPhi@ n - 2 n, {n, #}]] &[10^5] (* Michael De Vlieger, Nov 30 2016 *)