A273018 Ramanujan's largely composite numbers having 7 as the greatest prime divisor.

84, 168, 336, 420, 504, 630, 672, 840, 1260, 1680, 2520, 3360, 3780, 4200, 5040, 7560, 10080, 12600, 15120, 20160, 25200, 30240, 37800, 40320, 45360, 50400, 75600, 151200

Offset: 1

Author

Vladimir Shevelev and Peter J. C. Moses, May 13 2016

Keywords

• nonn
• fini
• full

Comments

By the theorem in A273015, the sequence is finite.

Crossrefs

Cf. A067128, A273015, A273016.

Programs

Mathematica

a = {}; b = {0}; Do[If[# >= Max@ b, AppendTo[a, k] && AppendTo[b, #]] &@ DivisorSigma[0, k], {k, 10^7}]; Select[a, FactorInteger[#][[-1, 1]] == 7 &] (* Michael De Vlieger, May 13 2016 *)