OFFSET
1,1
COMMENTS
Obviously such numbers need to have at least 10 x 2 = 20 digits, but the smallest solution a(1)=2^56*3^12 has actually 5 digits "3", and 2 of each of the other digits.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..40
J. Merickel, Conjecture, Sept. 2012
James Merickel and others, Conjecture, digest of 30 messages in primenumbers Yahoo group, Sep 16, 2012 - Jul 7, 2014.
PROG
(PARI) is_A216854(n)=my(t=divrem(n, 10), c=vector(10)); until(!t=divrem(t[1], 10), c[t[2]+1]++); vecmin(isprime(c)) && return(c)
(PARI) prDigits(n)=my(d=digits(n), v=vector(10)); for(i=1, #d, v[d[i]+1]++); for(i=1, 10, if(!isprime(v[i]), return(0))); 1
list(lim)=my(v=List(), t); for(a=0, log(lim+.5)\log(3), t=3^a; while(t<=lim, if(prDigits(t), listput(v, t)); t<<=1)); vecsort(Vec(v)) \\ Charles R Greathouse IV, Sep 19 2013
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Sep 17 2012
STATUS
approved