The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A263477 Total number of n-digit positive integers with multiplicative digital root value 2. 7
 1, 8, 68, 466, 2670, 13460, 69420, 417722, 3025242, 21873040, 136901413, 722201372, 3271729383, 13114173697, 48104723380, 167526488628, 574289772576, 1988721563904, 7000834741144, 24759698208450, 86342520209963, 292206955736762, 950480594161453 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First differences of A263471. LINKS Hiroaki Yamanouchi, Table of n, a(n) for n = 1..50 Eric Weisstein's World of Mathematics, Multiplicative Digital Root FORMULA A263476(n) + A000012(n) + a(n) + A000027(n) + A263478(n) + A263479(n) + A263480(n) + A000027(n) + A263481(n) + A000217(n) = A052268(n). MATHEMATICA Last /@ Tally@ IntegerLength@ Select[Range@ 1000000, FixedPoint[Times @@ IntegerDigits@ # &, #] == 2 &] (* Michael De Vlieger, Oct 21 2015 *) PROG (PARI) t(k) = {while(k>9, k=prod(i=1, #k=digits(k), k[i])); k} a(n) = sum(i=10^(n-1), 10^n - 1, if(t(i) == 2, 1, 0)); \\ Altug Alkan, Oct 19 2015 CROSSREFS Cf. A031347, A034049, A051813, A263471. Sequence in context: A050841 A208947 A296670 * A249390 A190510 A282563 Adjacent sequences: A263474 A263475 A263476 * A263478 A263479 A263480 KEYWORD nonn,base AUTHOR Martin Renner, Oct 19 2015 EXTENSIONS a(9)-a(23) from Hiroaki Yamanouchi, Oct 25 2015 STATUS approved

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

Last modified May 31 22:36 EDT 2023. Contains 363068 sequences. (Running on oeis4.)