A278374 - OEIS

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

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OFFSET

1,2

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.

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 *)

CROSSREFS

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

Sequence in context: A126233 A059889 A058011 * A300658 A366557 A089330

Adjacent sequences: A278371 A278372 A278373 * A278375 A278376 A278377

KEYWORD

nonn

AUTHOR

David W. Wilson, Nov 19 2016

STATUS

approved