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A272698 Powers of 2 with exactly one even decimal digit. 1
2, 4, 8, 16, 32, 512 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The number of even digits of powers of 2 is more than 0. However, it seems there are few powers of 2 with 1 even digit.

If there are any other terms in this sequence, they are greater than 2^10^10. - Charles R Greathouse IV, May 04 2016

LINKS

Table of n, a(n) for n=1..6.

MATHEMATICA

Select[2^Range[0, 50000], Total@ Pick[DigitCount@ #, {0, 1, 0, 1, 0, 1, 0, 1, 0, 1}, 1] == 1 &] (* Michael De Vlieger, May 04 2016 *)

Select[2^Range[200], Count[IntegerDigits[#], _?EvenQ]==1&] (* Harvey P. Dale, Aug 20 2017 *)

PROG

(Ruby)

ary = []

s = 1

(1..10 ** 4).each{|i|

  s *= 2

  j = s.to_s.split('').map(&:to_i).select{|i| i % 2 == 0}.size

  ary << s if j == 1

}

p ary

(PARI) is(n)=my(d=digits(n)); n>1 && n>>valuation(n, 2)==1 && sum(i=1, #d, d[i]%2==0)==1 \\ Charles R Greathouse IV, May 04 2016

CROSSREFS

Sequence in context: A138814 A233424 A137181 * A036373 A119610 A121485

Adjacent sequences:  A272695 A272696 A272697 * A272699 A272700 A272701

KEYWORD

nonn,base

AUTHOR

Seiichi Manyama, May 04 2016

STATUS

approved

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Last modified May 20 12:33 EDT 2019. Contains 323422 sequences. (Running on oeis4.)