A066307 Nonprimes such that sum of digits equals product of digits.

1, 4, 6, 8, 9, 22, 123, 132, 213, 231, 312, 321, 1124, 1142, 1214, 1241, 1412, 1421, 2114, 4112, 4121, 11125, 11133, 11152, 11215, 11222, 11313, 11331, 11512, 11521, 12115, 12122, 12151, 12212, 12221, 13113, 13131, 13311, 15112, 15211, 21115

Offset

1,2

Links

Chai Wah Wu, Table of n, a(n) for n = 1..10000 (n = 1..516 from Harry J. Smith)

Example

321 = 3*107, 3 + 2 + 1 = 6 = 3*2*1.

Mathematica

sdpdQ[n_]:=Module[{idn=IntegerDigits[n]}, Total[idn]==Times@@idn]; Module[ {upto=25000, cs}, cs=Complement[Range[upto], Prime[Range[PrimePi[upto]]]]; Select[cs, sdpdQ]] (* Harvey P. Dale, Oct 14 2014 *)

Prog

(PARI) SumD(x)= { local(s=0); while (x>9, s+=x%10; x\=10); return(s + x) } ProdD(x)= { local(p=1); while (x>9 && p>0, p*=x%10; x\=10); return(p*x) } { n=0; for (m=1, 10^9, if (isprime(m), next); if (SumD(m)==ProdD(m), write("b066307.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 09 2010

Crossrefs

Composites and 1 from A034710.

Cf. A034710, A066306.

Sequence in context: A078337 A046351 A161732 * A287198 A099071 A156673

Adjacent sequences: A066304 A066305 A066306 * A066308 A066309 A066310

Keyword

base,nonn

Author

Labos Elemer, Dec 13 2001

Status

approved