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 A076649 Number of digits required to write the prime factors of n. 6
 0, 1, 1, 2, 1, 2, 1, 3, 2, 2, 2, 3, 2, 2, 2, 4, 2, 3, 2, 3, 2, 3, 2, 4, 2, 3, 3, 3, 2, 3, 2, 5, 3, 3, 2, 4, 2, 3, 3, 4, 2, 3, 2, 4, 3, 3, 2, 5, 2, 3, 3, 4, 2, 4, 3, 4, 3, 3, 2, 4, 2, 3, 3, 6, 3, 4, 2, 4, 3, 3, 2, 5, 2, 3, 3, 4, 3, 4, 2, 5, 4, 3, 2, 4, 3, 3, 3, 5, 2, 4, 3, 4, 3, 3, 3, 6, 2, 3, 4, 4, 3, 4, 3, 5, 3, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..1000 FORMULA a(n) is completely additive: a(m*n) = a(m)+a(n) for all integers m, n >= 1, with a(1)=0 and a(p^e) = e*floor(log_10(10*p)), p prime. - Diego Torres (torresvillarroel(AT)hotmail.com), Oct 26 2002 Totally additive with a(p) = A055642(p). EXAMPLE 12 = 2*2*3 so a(12)=3. MATHEMATICA Join[{0}, Table[Total[IntegerLength[#]&/@(Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[n]])], {n, 2, 120}]] (* Harvey P. Dale, Mar 10 2018 *) PROG (PARI) a(n)=my(f=factor(n)); sum(i=1, #f[, 1], #Str(f[i, 1])*f[i, 2]) \\ Charles R Greathouse IV, Jul 24 2012 CROSSREFS Cf. A055642. Sequence in context: A344589 A153024 A066921 * A157235 A086289 A077807 Adjacent sequences: A076646 A076647 A076648 * A076650 A076651 A076652 KEYWORD base,nonn AUTHOR Jeff Burch, Oct 24 2002 EXTENSIONS a(1) added, a(40) corrected by Charles R Greathouse IV, Jul 24 2012 STATUS approved

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Last modified May 28 18:29 EDT 2024. Contains 372919 sequences. (Running on oeis4.)