A274774 Least k such that sigma(k*n)/tau(k*n) = sigma(k*n+1)/tau(k*n+1), or 0 if no such k exists.

5, 7, 895, 1363, 1, 3353, 2, 2589, 1007, 10341, 1265, 1726, 7, 1, 179, 6634, 10052, 5745, 86, 53389, 958, 12165, 58, 863, 649, 250017, 2395, 6103, 46, 3447, 2714, 3317, 8110, 5026, 22653, 2812637, 94, 43, 16795, 58069, 61693, 479, 38, 52790, 1437, 29, 74, 2027510, 122367, 70545

Offset: 1

Author

Altug Alkan, Jul 28 2016

Keywords

• nonn

Comments

Corresponding averages are 3, 6, 540, 840, 3, 2880, 6, 3240, 1170, 8640, 1596, 3240, 28, 6, 540, 9072, 15120, 8640, 330, 55440, 2880, 21924, 270, 3240, 1860, 875070, 7200, ...

Examples

			a(13) = 7 because sigma(7*13)/tau(7*13) = sigma(7*13+1)/tau(7*13+1).
		

Crossrefs

Cf. A238380.

Programs

Mathematica

a[n_] := Block[{k=1}, While[! Equal @@ (DivisorSigma[1, n*k + {0,1}] / DivisorSigma[ 0, n*k + {0,1}]), k++]; k]; Array[a, 20] (* Giovanni Resta, Jul 28 2016 *)

PARI

a(n) = {my(k=1); while (sigma(k*n)/numdiv(k*n) != sigma(k*n+1)/numdiv(k*n+1), k++); k; }