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 A144098 a(1)=1. a(n) = the smallest positive multiple of a(n-1) that contains the binary representations of all positive integers <= n at least once each in its binary representation. 2
 1, 2, 6, 12, 108, 108, 756, 1512, 37800, 37800, 945000, 945000, 945000, 945000, 10395000, 20790000, 602910000, 23513490000, 23513490000, 23513490000, 23513490000, 23513490000, 23513490000, 23513490000, 23513490000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(4) = 12. Checking the multiples of 12 to see when 1,2,3,4,5 (1,10,11,100,101 in binary) first all occur: 12*1 = 12 = 1100 in binary, contains 1, 2(10 in binary), 3(11 in binary), 4(100 in binary), but not 5(101 in binary). 12*2=24 = 11000 in binary, contains 1 through 4, but not 5. 12*3 = 36 = 100100 in binary, doesn't contain 3(11) or 5(101). 12*4 = 48 = 110000 in binary, doesn't contain 5. 12*5=60 =111100 in binary, doesn't contain 5. 12*6 = 72 = 1001000 in binary, doesn't contain 3 or 5. 12*7= 84 = 1010100 in binary, does not contain 3. 12*8 = 96 = 1100000 in binary, doesn't contain 5. But 12*9 = 108 = 1101100 in binary: Contains 1, like so (1)101100; contains 2, like so 1(10)1100; contains 3, (11)01100; contains 4, 1101(100); and contains 5, 1(101)100. So a(5) = 108. MAPLE A144098 := proc(n) option remember ; local aprev, k, gooda, a, ntst ; if n = 1 then RETURN(1) ; fi; aprev := procname(n-1) ; for k from 1 do a := aprev*k ; gooda := true ; for ntst from 1 to n do if not verify(convert(a, base, 2), convert(ntst, base, 2), 'superlist') then gooda := false ; break ; fi; od: if gooda then RETURN(a) ; fi; od: end: for n from 1 to 40 do printf("%d, ", A144098(n)) ; od: # R. J. Mathar, Sep 17 2008 CROSSREFS Cf. A144099. Sequence in context: A141288 A062954 A038787 * A259140 A075071 A250269 Adjacent sequences:  A144095 A144096 A144097 * A144099 A144100 A144101 KEYWORD base,nonn AUTHOR Leroy Quet, Sep 10 2008 EXTENSIONS More terms from R. J. Mathar, Sep 17 2008 STATUS approved

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Last modified April 21 10:30 EDT 2019. Contains 322328 sequences. (Running on oeis4.)