This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A242751 Semiprimes having only holey digits (0,4,6,8,9). 1

%I

%S 4,6,9,46,49,69,86,94,446,466,469,489,649,669,689,694,698,699,849,866,

%T 869,886,889,898,899,949,989,998,4006,4009,4069,4406,4449,4469,4486,

%U 4489,4499,4609,4666,4694,4699,4846,4849,4894,4946,4989,6009,6046,6049,6098

%N Semiprimes having only holey digits (0,4,6,8,9).

%H K. D. Bajpai, <a href="/A242751/b242751.txt">Table of n, a(n) for n = 1..8612</a>

%e 4609 = 11 * 419 is semiprime and has only holey digits 4, 6, 0 and 9. Hence it is in the sequence.

%e 4849 = 13 * 373 is semiprime and has only holey digits 4, 8, 4 and 9. Hence it is in the sequence.

%t c = 0; Do[a = PrimeOmega[n];If[a==2&& Intersection[IntegerDigits[n],{1,2,3,5,7}]=={},c++; Print[c, " ", n]], {n, 2*10^7}]

%t Select[FromDigits/@Tuples[{0,4,6,8,9},4],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Sep 08 2017 *)

%Y Cf. A001358, A061372.

%K nonn,base

%O 1,1

%A _K. D. Bajpai_, May 21 2014

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.

Last modified October 15 00:14 EDT 2019. Contains 328025 sequences. (Running on oeis4.)