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 A078226 a(1) = 1, a(n+1) is the smallest odd multiple of a(n) (other than a(n) itself) in which the digits are alternately even and odd. 4
 1, 3, 9, 27, 81, 567, 8505, 76545, 9874305, 6763898925, 41672381276925, 25432529276163496725, 6947294789656341278149816125, 2341412581496361870123890149638785410125 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(6) = 567 = 7*a(5); the digits alternate odd, even, odd. MAPLE isA030141 := proc(n) local dgs, i ; dgs := convert(n, base, 10) ; for i from 1 to nops(dgs)-1 do if ( op(i, dgs)+op(i+1, dgs)) mod 2 = 0 then RETURN(false) ; fi ; od ; RETURN(true) ; end: A078226 := proc(nmax) local a, f; a := [1] ; while nops(a) < nmax do f := 3 ; while true do if isA030141(f*op(-1, a)) then a := [op(a), f*op(-1, a)] ; print(op(-1, a)) ; break ; fi ; f := f+2 ; od ; od ; end: A078226(13) ; - R. J. Mathar, Mar 01 2007 CROSSREFS Cf. A078221, A078222, A078223, A078224, A078225, A078227. Sequence in context: A050733 A079846 A067500 * A083591 A052917 A099786 Adjacent sequences:  A078223 A078224 A078225 * A078227 A078228 A078229 KEYWORD base,nonn AUTHOR Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 23 2002 EXTENSIONS More terms from Sascha Kurz, Jan 30 2003 a(12) from R. J. Mathar, Mar 01 2007 a(13), a(14) from Max Alekseyev, May 12 2010 STATUS approved

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