login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=1..14.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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