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

Author

Jonathan Frech, Apr 19 2017

Keywords

• nonn
• base

Links

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

Crossrefs

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

Programs

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 *)

PARI

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

Extensions

More terms from Michel Marcus, Apr 20 2017