OFFSET

1,1

COMMENTS

A subsequence of A130694.

Motivated by J. Merickel's question about the least power of 2 in which all digits 0-9 occur a prime number of times. The first 4 terms of this sequence are all such that this is the case for all but one digit; see Examples.

Beyond 184, the numbers 195-197 and 229 are the only exponents < 10^4 which are not in this sequence. Is 229 the largest such number?

LINKS

J. Merickel, Are these new questions?, Yahoo! group "primenumbers", Aug 24 2012.

James Merickel, Are these new questions?, message 24399 in primenumbers Yahoo group, Aug 24, 2012.

EXAMPLE

Digit counts for 2^n:

.

n\d| 0 1 2 3 4 5 6 7 8 9

---+-----------------------------

88| 5 2 2 2 3 3 2 2 4* 2

104| 5 3 6* 2 3 2 5 2 2 2

113| 5 3 3 2 3 5 4* 3 2 5

114| 3 7 2 5 4* 2 2 2 5 3

.

*nonprime counts

PROG

(PARI) is_A215830(n)={my(c=vector(10), N=[1<<n, 0]); while(N=divrem(N[1], 10), c[N[2]+1]++); vecmin(c)>1}

CROSSREFS

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Aug 25 2012

STATUS

approved