A216872 Numbers n such that 2^n in decimal has at least 8 of the digits 0-9 appearing a prime number times.

59, 67, 88, 104, 107, 108, 113, 114, 118, 120, 141, 146, 150, 156, 190, 214, 444, 880628

Offset

1,1

Comments

Heuristically, all digits appear a prime number of times for an infinite number of values of n. A216873 contains the subset with 9 in place of 8.

a(19) > 5000000. - James G. Merickel, Apr 17 2015

Links

Table of n, a(n) for n=1..18.

Prog

(PARI)
/* program prints asterisks for values giving 9 instead of just 8,
  and stops if all digits appear a prime number of times. */
{ a=2; p=1; while(p, b=a; c=vectorsmall(10); while(b,
d=b%10; b\=10; c[d+1]++; next()); e=3; for(i=1, 10,
if(isprime(c[i])==0, e--; if(e==0, break()))); if(e,
print1(p); if(e>1, print1("*"); if(e==3, break())); print1("\n"));
p++; a+=a; next()) }

Crossrefs

Cf. A216873.

Sequence in context: A048988 A087766 A096339 * A235225 A015979 A065208

Adjacent sequences: A216869 A216870 A216871 * A216873 A216874 A216875

Keyword

nonn,base,hard

Author

James G. Merickel, Sep 18 2012

Extensions

a(18) added by James G. Merickel, Jul 07 2013

Status

approved