OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000 (first 150 terms from Harry J. Smith; a(0) modified by M. F. Hasler).
MATHEMATICA
a = {}; Do[k = 0; While[ Count[ IntegerDigits[4^k], 0] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Module[{nn=750, p4}, p4=Table[{n, DigitCount[4^n, 10, 0]}, {n, nn}]; Transpose[ Table[ SelectFirst[p4, #[[2]]==i&], {i, 0, 50}]][[1]]] (* The program uses the SelectFirst function from Mathematica version 10 *) (* Harvey P. Dale, May 20 2016 *)
PROG
(PARI) Count(x, d)= { local(c, f); c=0; while (x>9, f=x-10*(x\10); if (f==d, c++); x\=10); if (x==d, c++); return(c) } { for (n=0, 150, a=0; while (Count(4^a, 0) != n, a++); write("b063575.txt", n, " ", a) ) } \\ Harry J. Smith, Aug 26 2009
(PARI) A063575(n)=for(k=n, oo, #select(d->!d, digits(4^k))==n&&return(k)) \\ M. F. Hasler, Jun 14 2018
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
STATUS
approved