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
 4, 6, 9, 46, 49, 69, 86, 94, 446, 466, 469, 489, 649, 669, 689, 694, 698, 699, 849, 866, 869, 886, 889, 898, 899, 949, 989, 998, 4006, 4009, 4069, 4406, 4449, 4469, 4486, 4489, 4499, 4609, 4666, 4694, 4699, 4846, 4849, 4894, 4946, 4989, 6009, 6046, 6049, 6098 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS K. D. Bajpai, Table of n, a(n) for n = 1..8612 EXAMPLE 4609 = 11 * 419 is semiprime and has only holey digits 4, 6, 0 and 9. Hence it is in the sequence. 4849 = 13 * 373 is semiprime and has only holey digits 4, 8, 4 and 9. Hence it is in the sequence. MATHEMATICA 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}] Select[FromDigits/@Tuples[{0, 4, 6, 8, 9}, 4], PrimeOmega[#]==2&] (* Harvey P. Dale, Sep 08 2017 *) CROSSREFS Cf. A001358, A061372. Sequence in context: A257652 A107665 A085733 * A107342 A086698 A317248 Adjacent sequences:  A242748 A242749 A242750 * A242752 A242753 A242754 KEYWORD nonn,base AUTHOR K. D. Bajpai, May 21 2014 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.

Last modified June 18 15:25 EDT 2019. Contains 324213 sequences. (Running on oeis4.)