OFFSET
1,2
EXAMPLE
2^7 = 128 is the first power of 2 with 3 different digits. Thus a(3) = 7.
MATHEMATICA
dd[n_]:=Count[DigitCount[2^n], _?(#>0&)]; Table[SelectFirst[Table[{n, dd[n]}, {n, 70}], #[[2]] == k&], {k, 10}][[All, 1]] (* Harvey P. Dale, Jan 22 2023 *)
PROG
(PARI) a(n)=for(k=1, 10^3, st=2^k; if(#digits(st)>=n, c=0; for(i=0, 9, for(j=1, #digits(st), if(digits(st)[j]==i, c++; break))); if(c==n, return(k))))
n=1; while(n<11, print1(a(n), ", "); n++)
CROSSREFS
KEYWORD
nonn,base,full,fini
AUTHOR
Derek Orr, Jun 14 2014
STATUS
approved