A280032 Composite numbers n such that the number of digits in n equals the total number of digits in the prime power factorization of n.

10, 14, 15, 16, 21, 25, 27, 32, 35, 49, 64, 81, 105, 106, 111, 112, 115, 118, 119, 121, 122, 123, 129, 133, 134, 135, 141, 142, 145, 146, 147, 155, 158, 159, 160, 161, 162, 166, 169, 175, 177, 178, 183, 185, 189, 192, 194, 201, 203, 205, 213, 215, 217, 219, 224, 235, 237, 245, 249, 250

Offset: 1

Author

N. J. A. Sloane, Dec 27 2016

Keywords

• nonn
• base

Comments

Suggested by A279070.

Primes are excluded by decree.

In the prime power factorization of p we write p rather than p^1.

Examples

			10 = 2*5 is a term (both have 2 digits).
27 = 3^3 is a term (both have 2 digits).
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5100

Crossrefs

Cf. A279070.

Programs

Mathematica

ndf[n_]:=Total[IntegerLength/@Select[Flatten[FactorInteger[n]],#!=1&]];
Select[Range[250],!PrimeQ[#]&&IntegerLength[#]==ndf[#]&] (* Ivan N. Ianakiev, Dec 28 2016 *)

Extensions

a(14)-a(60) from Ivan N. Ianakiev, Dec 28 2016