A278374 a(n) = smallest k with sigma(k) + phi(k) - 2k = A278373(n).

1, 4, 6, 8, 27, 125, 16, 12, 18, 20, 28, 50, 63, 32, 44, 98, 52, 24, 68, 42, 242, 40, 70, 338, 54, 36, 56, 116, 78, 578, 165, 130, 722, 135, 48, 164, 114, 1058, 104, 188, 285, 138, 100, 80, 230, 1682, 136, 128, 60, 1922, 244, 152, 741, 112, 225, 351, 72, 284, 2738, 90, 84, 651, 222, 3362, 711, 332, 3698, 459, 196, 96, 162, 356

Offset: 1

Author

David W. Wilson, Nov 19 2016

Keywords

• nonn

Links

• David W. Wilson, Table of n, a(n) for n = 1..10000
• n = 24 is the smallest number with sigma(n) + phi(n) - 2n = 20 = A278383(18), so a(18) = 24.

Crossrefs

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

Programs

Mathematica

Function[w, Map[Position[w, #][[1, 1]] &, Take[#, 72]] &@ Union@ w]@ Table[DivisorSigma[1, n] + EulerPhi@ n - 2 n, {n, 10^4}] (* Michael De Vlieger, Nov 30 2016 *)