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

1,1

Comments

By the theorem in A273015, the sequence is finite.

Links

Table of n, a(n) for n=1..28.

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 *)

Crossrefs

Cf. A067128, A273015, A273016.

Sequence in context: A260703 A044254 A044635 * A260705 A295596 A287118

Adjacent sequences: A273015 A273016 A273017 * A273019 A273020 A273021

Keyword

nonn,fini,full

Author

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

Status

approved