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 A078227 a(1) = 2, a(n+1) is the smallest multiple of a(n) such that the digits are alternately odd and even. The unit digit is always even and parity alternates. 4
 2, 4, 8, 16, 32, 96, 672, 45696, 2787456, 270383232, 507238943232, 27274745216527872, 141232121898569036783616, 216567470725252501672125832323072 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(7) = 672 = 7*a(6) = 7*96. Starting with the unit digit the digits in 672 are alternately even and odd. MAPLE isAltr := proc(n) local nshft, osgn, sgn ; nshft := n ; osgn := ( n mod 10 ) mod 2 ; while nshft >= 10 do nshft := floor(nshft/10) ; sgn := ( nshft mod 10 ) mod 2 ; if sgn = osgn then RETURN(false) ; fi ; osgn := sgn ; od ; RETURN(true) ; end: A078227 := proc(prev) local m; m := 2 ; while true do if isAltr(m*prev) then RETURN(m*prev) ; fi ; m := m+1 ; od ; end: n := 2 : while true do print(n) ; n := A078227(n) : od : # R. J. Mathar, Nov 12 2006 PROG (Python) A078227_list = [2] for _ in range(20): ....x = A078227_list[-1] ....y = x ....while True: ........y += x ........s = str(y) ........for j in range(len(s)-1, -1, -2): ............if not s[j] in ('0', '2', '4', '6', '8'): ................break ........else: ............for k in range(len(s)-2, -1, -2): ................if not s[k] in ('1', '3', '5', '7', '9'): ....................break ............else: ................A078227_list.append(y) ................break # Chai Wah Wu, Nov 06 2014 CROSSREFS Cf. A078221, A078222, A078223, A078224, A078225, A078226, A078228. Sequence in context: A290301 A195458 A264656 * A250073 A260873 A138814 Adjacent sequences:  A078224 A078225 A078226 * A078228 A078229 A078230 KEYWORD base,more,nonn AUTHOR Amarnath Murthy, Nov 23 2002 EXTENSIONS More terms from R. J. Mathar, Nov 12 2006 a(13) and a(14) from Donovan Johnson, Mar 09 2008 STATUS approved

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Last modified August 14 12:15 EDT 2022. Contains 356116 sequences. (Running on oeis4.)