The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A063575 Smallest k such that 4^k has exactly n 0's in its decimal representation. 11
 0, 5, 21, 35, 47, 44, 50, 51, 103, 99, 121, 125, 126, 175, 166, 131, 185, 153, 184, 223, 272, 232, 248, 336, 233, 306, 315, 384, 314, 327, 333, 373, 393, 399, 454, 457, 504, 453, 484, 506, 621, 494, 510, 639, 522, 557, 560, 559, 716, 609, 629 (list; graph; refs; listen; history; text; internal format)
 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 Cf. A031146 (analog for 2^k), A063555 (for 3^k), A063585 (for 5^k), A063596 (for 6^k), A063606 (for 7^k), A063616 (for 8^k). Sequence in context: A317693 A145026 A039561 * A302873 A170837 A170876 Adjacent sequences:  A063572 A063573 A063574 * A063576 A063577 A063578 KEYWORD base,nonn AUTHOR Robert G. Wilson v, Aug 10 2001 EXTENSIONS a(0) changed to 0 as in A031146, A063555, ... by M. F. Hasler, Jun 14 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 25 19:09 EST 2020. Contains 331249 sequences. (Running on oeis4.)