The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A066042 n divided by ((sum of digits of n) times (product of digits of n)) is prime. 2
 12, 111, 216, 432, 41112, 81216, 186624, 248832, 311472, 316224, 341712, 422144, 714112, 1131111, 1131732, 1191915, 1211328, 1292112, 1418112, 2192832, 3112128, 4331232, 11127424, 11311272, 18122112, 21111192, 26726112, 28422144, 34338816 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS David A. Corneth, Table of n, a(n) for n = 1..1744 (first 469 terms from Harry J. Smith and Chai Wah Wu) FORMULA Sum digits of n; take product of digits of n; multiply sum by product and divide into n. If prime, add to sequence. EXAMPLE a(2) = 111 because 1+1+1 = 3 and 1*1*1 = 1 and 3*1 = 3 and 111/3 = 37 and 37 is prime. [corrected by Harry J. Smith, Nov 08 2009] MATHEMATICA ndspQ[n_]:=Module[{idn=IntegerDigits[n]}, FreeQ[idn, 0]&&PrimeQ[n/(Total[ idn]Times@@idn)]]; Select[Range[35*10^6], ndspQ] (* Harvey P. Dale, Feb 09 2015 *) PROG (PARI) ProdD(x)= { local(p=1); while (x>9 && p>0, p*=x%10; x\=10); return(p*x) } SumD(x)= { local(s=0); while (x>9, s+=x%10; x\=10); return(s + x) } { n=0; for (m=1, 10^12, p=ProdD(m); if (p == 0, next); f=m/(SumD(m)*p); if (frac(f)==0 && isprime(f), write("b066042.txt", n++, " ", m); if (n==100, return)) ) } \\ Harry J. Smith, Nov 08 2009 CROSSREFS Cf. A038369, A049102, A066146. Sequence in context: A049102 A075231 A085773 * A153597 A036733 A253091 Adjacent sequences:  A066039 A066040 A066041 * A066043 A066044 A066045 KEYWORD easy,nonn,base AUTHOR Enoch Haga, Dec 13 2001 EXTENSIONS Checked to over 10^8 (110508539) without finding another example. Offset 1 from Harry J. Smith, Nov 08 2009 Should have found 34338816, 37121112, and 41174112 < 10^8. Term a(29) from Harry J. Smith, Nov 08 2009 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.

Last modified December 6 20:22 EST 2021. Contains 349567 sequences. (Running on oeis4.)