login
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.
1
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
1,1
COMMENTS
Suggested by A279070.
Primes are excluded by decree.
In the prime power factorization of p we write p rather than p^1.
LINKS
EXAMPLE
10 = 2*5 is a term (both have 2 digits).
27 = 3^3 is a term (both have 2 digits).
MATHEMATICA
ndf[n_]:=Total[IntegerLength/@Select[Flatten[FactorInteger[n]], #!=1&]];
Select[Range[250], !PrimeQ[#]&&IntegerLength[#]==ndf[#]&] (* Ivan N. Ianakiev, Dec 28 2016 *)
CROSSREFS
Cf. A279070.
Sequence in context: A335169 A164936 A102361 * A227010 A246449 A121836
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Dec 27 2016
EXTENSIONS
a(14)-a(60) from Ivan N. Ianakiev, Dec 28 2016
STATUS
approved