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A272898 Numbers n such that 2^n has equal numbers of odd and even decimal digits. 2
4, 5, 13, 30, 51, 64, 65, 77, 78, 130, 144, 171, 185, 199, 210, 239, 259, 263, 271, 296, 312, 369, 389, 391, 429, 437, 449, 457, 483, 490, 496, 498, 502, 551, 582, 583, 628, 648, 677, 709, 721, 744, 750, 776, 796, 874, 923, 943 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..1000

EXAMPLE

4 is a member since 2^4 = 16 has 1 odd digit and 1 even digit.

12 is not a member since 4096 has 1 odd digit and 3 even digits.

13 is a member since 8192 has 2 odd digits and 2 even digits.

MATHEMATICA

ok[n_] := Block[{d=IntegerDigits[2^n]}, EvenQ@ Length@ d && 0 == Plus @@ ((-1)^d) ]; Select[ Range@ 10000, ok] (* Giovanni Resta, May 09 2016 *)

PROG

(PARI) is(n)=my(d=digits(2^n)); #d%2==0 && sum(i=1, #d, (-1)^d[i])==0 \\ Charles R Greathouse IV, May 09 2016

CROSSREFS

Cf. A000079.

Sequence in context: A140683 A304599 A071341 * A102981 A257487 A249394

Adjacent sequences:  A272895 A272896 A272897 * A272899 A272900 A272901

KEYWORD

nonn,base

AUTHOR

Seiichi Manyama, May 09 2016

STATUS

approved

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Last modified August 5 08:48 EDT 2021. Contains 346464 sequences. (Running on oeis4.)