A285494 Numbers k such that digit sum of k = number of distinct prime factors of k.

20, 30, 102, 120, 200, 300, 1002, 1200, 2000, 2001, 2002, 3000, 3010, 10001, 10002, 10011, 10030, 10120, 11001, 11020, 11110, 12000, 20000, 20001, 21010, 30000, 30030, 30100, 100001, 100030, 100101, 100130, 100210, 100300, 101001, 101101, 101200, 102102, 110001, 110200

Offset

1,1

Links

Giovanni Resta, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[2, 10000], Total[IntegerDigits[#]]==Length[FactorInteger[#]]&] (* or *)
nd = 10; s = 1; Sort@ Flatten@ Reap[ While[ Times @@ Prime[ Range@ s] < 10^nd, pa = IntegerPartitions[s, {nd}, Range[0, 9]]; Do[Sow@ Select[ FromDigits /@ Permutations[p], PrimeNu[#] == s &], {p, pa}]; s++]][[2, 1]] (* terms < 10^10, Giovanni Resta, Apr 21 2017 *)

Prog

(PARI) isok(n) = sumdigits(n) == omega(n); \\ Michel Marcus, Apr 20 2017

Crossrefs

Cf. A001221, A007953, A057531, A057532, A050689, A070274, A070275, A063737, A067077.

Sequence in context: A268984 A359002 A066214 * A120210 A181639 A166631

Adjacent sequences: A285491 A285492 A285493 * A285495 A285496 A285497

Keyword

nonn,base

Author

Jonathan Frech, Apr 19 2017

Extensions

More terms from Michel Marcus, Apr 20 2017

Status

approved