1,1

a(n)=Min{x; sigma[x]/2x < 1 and A001221(x)=n}

n=5: a(n)=36465=3.5.11.13.17; sigma[36465]=72576<72930=2.sigma[a(n)].

q[x_] := Apply[Times, Table[Prime[w], {w, 1, x}]]; q[0]=1; Do[s=DivisorSigma[1, n]; If[Greater[2*n, s]&&Equal[lf[n], j]&& Equal[fl, 1], Print[{n, {s, 2*n}, j}]; fl=0], {n, q[j], q[j+2]}], {j, 1, 6}]

Cf. A000203, A002110, A005100.

Sequence in context: A135058 A005799 A000595 this_sequence A049538 A127728 A003222

Adjacent sequences: A087231 A087232 A087233 this_sequence A087235 A087236 A087237

nonn

Labos E. (labos(AT)ana.sote.hu), Sep 01 2003