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Search: id:A078227
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| A078227 |
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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. |
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+0
4
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| 2, 4, 8, 16, 32, 96, 672, 45696, 2787456, 270383232, 507238943232, 27274745216527872, 141232121898569036783616, 216567470725252501672125832323072
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(7) = 672 = 7*a(6) = 7*96. Starting with the unit digit the digits in 672 are alternately even and odd.
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MAPLE
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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 (mathar(AT)strw.leidenuniv.nl), Nov 12 2006
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CROSSREFS
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Cf. A078221, A078222, A078223, A078224, A078225, A078226, A078228, A077229.
Adjacent sequences: A078224 A078225 A078226 this_sequence A078228 A078229 A078230
Sequence in context: A100139 A076766 A035523 this_sequence A138814 A137181 A036373
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KEYWORD
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base,more,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 23 2002
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 12 2006
a(13) and a(14) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Mar 09 2008
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