A120700 a(n) is the least refactorable number k having the n-th prime as its greatest prime factor.

2, 9, 40, 56, 88, 104, 136, 152, 184, 232, 248, 296, 328, 344, 376, 424, 472, 488, 536, 568, 584, 632, 664, 712, 776, 808, 824, 856, 872, 904, 1016, 1048, 1096, 1112, 1192, 1208, 1256, 1304, 1336, 1384, 1432, 1448, 1528, 1544, 1576, 1592, 1688, 1784, 1816

Offset: 1

Author

Walter Kehowski and Robert G. Wilson v, Jun 28 2006

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A033950, A036878.

Programs

Mathematica

f[n_] := Block[{a = Mod[n, DivisorSigma[0, n]], b = PrimePi[FactorInteger[n][[ -1, 1]]]}, {a, b}]; t = Table[0, {100}]; Do[c = f[n]; If[c[[1]] == 0 && t[[c[[2]]]] == 0, t[[c[[2]]]] = n], {n, 2, 1831}]