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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A145746 Numbers n such that sum of the proper divisors of n is product of digits of n. 2
6, 11, 778, 11735953 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All repunit primes are in the sequence. So A004022 is a subsequence of this sequence.

All terms beyond a(3) are coprime to 6, and of course all terms are zerofree (A052382). a(5) > 10^11. - Charles R Greathouse IV, Nov 03 2014

a(5) > 2*10^12. - Giovanni Resta, Aug 30 2018

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

sigma(11735953)=sigma(883*13291)=11735953+(13291+883+1)=11735953+

1*1*7*3*5*9*5*3 so 11735953 is in the sequence.

MATHEMATICA

Do[If[DivisorSigma[1, n]-n==Apply[Times, IntegerDigits[n]], Print[n]], {n, 50000000}]

PROG

(PARI) is(n)=my(d=digits(n), p=prod(i=1, #d, d[i])); p>0 && p+n==sigma(n) \\ Charles R Greathouse IV, Nov 03 2014

CROSSREFS

Subsequence of A052382.

Cf. A004022.

Sequence in context: A136980 A083834 A136978 * A024267 A028584 A243017

Adjacent sequences:  A145743 A145744 A145745 * A145747 A145748 A145749

KEYWORD

base,more,nice,nonn

AUTHOR

Farideh Firoozbakht, Oct 27 2008

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 19 03:48 EST 2019. Contains 329310 sequences. (Running on oeis4.)