The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A046446 Nonprimes whose prime factors contain only odd digits. 0
 1, 9, 15, 21, 25, 27, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 75, 77, 81, 85, 91, 93, 95, 99, 105, 111, 117, 119, 121, 125, 133, 135, 143, 147, 153, 155, 159, 165, 169, 171, 175, 177, 185, 187, 189, 195, 209, 213, 217, 219, 221, 225, 231, 237, 243, 245, 247, 255 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..58. EXAMPLE 247 = 13 * 19; 1, 3 and 9 are odd digits. MAPLE isA046446 := proc(n) if not isprime(n) then fset := numtheory[factorset](n) ; for f in fset do convert(convert(f, base, 10), set) ; if % intersect {0, 2, 4, 6, 8} <> {} then return false; end if; end do: true ; else false; end if; end proc: for n from 1 to 260 do if isA046446(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Oct 02 2018 MATHEMATICA Select[Range[255], ! PrimeQ[#] && And @@ OddQ[Union[Flatten[IntegerDigits[First /@ FactorInteger[#]]]]] &] (* Jayanta Basu, Jun 24 2013 *) CROSSREFS Subsequence of A014076. Sequence in context: A067800 A155474 A100819 * A046350 A225438 A175076 Adjacent sequences: A046443 A046444 A046445 * A046447 A046448 A046449 KEYWORD nonn,easy,base AUTHOR Patrick De Geest, Jul 15 1998 EXTENSIONS Definition clarified by Harvey P. Dale, Jul 07 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 13 17:32 EDT 2024. Contains 373391 sequences. (Running on oeis4.)