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 A263478 Total number of n-digit positive integers with multiplicative digital root value 4. 7
 1, 9, 55, 214, 615, 1451, 3829, 60180, 939045, 8732485, 56961531, 289887214, 1229099287, 4756606869, 24218431805, 233925901576, 2661527233449, 25685325408201, 203451565638511, 1356903584035110, 7832822232934951, 40022453239462639, 184228949831881593 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First differences of A263472. LINKS Hiroaki Yamanouchi, Table of n, a(n) for n = 1..50 FORMULA A263476(n) + A000012(n) + A263477(n) + A000027(n) + a(n) + A263479(n) + A263480(n) + A000027(n) + A263481(n) + A000217(n) = A052268(n). MATHEMATICA Last /@ Tally@ IntegerLength@ Select[Range@ 1000000, FixedPoint[Times @@ IntegerDigits@ # &, #] == 4 &] (* 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) == 4, 1, 0)); \\ Altug Alkan, Oct 19 2015 CROSSREFS Cf. A031347, A034051, A263472. Sequence in context: A299519 A068970 A141530 * A326249 A016269 A005770 Adjacent sequences:  A263475 A263476 A263477 * A263479 A263480 A263481 KEYWORD nonn,base AUTHOR Martin Renner, Oct 19 2015 EXTENSIONS a(9)-a(23) from Hiroaki Yamanouchi, Oct 25 2015 STATUS approved

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Last modified September 22 14:03 EDT 2020. Contains 337289 sequences. (Running on oeis4.)