login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A087234 Smallest deficient number with n distinct prime factors. 0
2, 10, 105, 1155, 36465, 969969, 37182145, 1078282205, 39896441585, 2668861960765, 183330286997165, 14415008697720995, 775932344695001065, 45780008337005062835, 3909612711980232366109, 261944051702675568529303, 18598027670889965365580513 (list; graph; refs; listen; history; text; internal format)
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

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

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 A049538

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 18 20:29 EDT 2018. Contains 313840 sequences. (Running on oeis4.)