A087234 Smallest deficient number with n distinct prime factors.

2, 10, 105, 1155, 36465, 969969, 37182145, 1078282205, 39896441585, 2668861960765, 183330286997165, 14415008697720995, 775932344695001065, 45780008337005062835, 3909612711980232366109, 261944051702675568529303, 18598027670889965365580513

Offset

1,1

Comments

From Donovan Johnson, Jan 25 2009: (Start)

a(14) <= 45780008337005062835;

a(15) <= 3909612711980232366109;

a(16) <= 261944051702675568529303. (End)

Links

Table of n, a(n) for n=1..17.

Formula

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

Example

For n=5: a(5) = 36465 = 3*5*11*13*17; sigma(36465) = 72576 < 72930 = 2*sigma(a(5)).

Mathematica

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}]

Crossrefs

Cf. A000203, A002110, A005100.

Sequence in context: A005799 A208730 A000595 * A273965 A273961 A365507

Adjacent sequences: A087231 A087232 A087233 * A087235 A087236 A087237

Keyword

nonn

Author

Labos Elemer, Sep 01 2003

Extensions

a(6) corrected and a(7)-a(13) from Donovan Johnson, Jan 25 2009

a(14)-a(17) from Jon E. Schoenfield, Jul 08 2018

Status

approved