A226363 Oblong numbers (A002378) whose sum of divisors is also an oblong number.

6, 20, 30, 306, 1722, 2862, 11772, 13572, 28730, 29756, 40602, 54056, 219492, 351056, 463080, 947702, 1391220, 1546292, 2043470, 7174362, 7703400, 11400752, 15104882, 19127502, 20155610, 113667582, 172173762, 314299712, 475654290, 555238532, 558447792, 562519806

Offset: 1

Author

Alex Ratushnyak, Jun 05 2013

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A000203, A002378, A083674.

Programs

Mathematica

oblongQ[n_] := IntegerQ[(-1 + Sqrt[1 + 4*n])/2]; s = Select[Range[24000], oblongQ[DivisorSigma[1, # (# + 1)]] &]; s * (s + 1) (* T. D. Noe, Jun 12 2013 *)