login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A230213 Odious numbers (A000069) which can be written as a product of two evil numbers (A001969). 5
25, 50, 69, 81, 87, 100, 115, 117, 138, 145, 162, 171, 174, 200, 213, 230, 234, 261, 265, 276, 285, 289, 290, 324, 333, 339, 342, 345, 348, 351, 355, 357, 369, 375, 385, 391, 400, 405, 415, 425, 426, 445, 460, 468, 475, 477, 493, 505, 522, 529, 530, 552, 555 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

Odious number 100 equals 5*20, such that 5 and 20 are evil. So, 100 is in the sequence.

MATHEMATICA

evilQ[n_] := EvenQ[DigitCount[n, 2][[1]]]; odiousQ[n_] := OddQ[DigitCount[n, 2][[1]]]; fQ[n_] := Module[{f, i}, If[PrimeQ[n], False, f = Select[Divisors[n], # > 1 && # <= Sqrt[n] &]; i = 1; While[i <= Length[f] && ! (evilQ[f[[i]]] && evilQ[n/f[[i]]]), i++]; i <= Length[f]]]; Select[Range[1000], odiousQ[#] && fQ[#] &] (* T. D. Noe, Oct 16 2013 *)

CROSSREFS

Cf. A000069, A001969.

Sequence in context: A118882 A085625 A116490 * A008607 A044077 A043350

Adjacent sequences:  A230210 A230211 A230212 * A230214 A230215 A230216

KEYWORD

nonn,base

AUTHOR

Vladimir Shevelev, Oct 11 2013

EXTENSIONS

Extended by T. D. Noe, Oct 16 2013

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 17 19:02 EDT 2019. Contains 327137 sequences. (Running on oeis4.)