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A043000
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Number of digits in all base-b representations of n, for 2 <= b <= n.
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5
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2, 4, 7, 9, 11, 13, 16, 19, 21, 23, 25, 27, 29, 31, 35, 37, 39, 41, 43, 45, 47, 49, 51, 54, 56, 59, 61, 63, 65, 67, 70, 72, 74, 76, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126
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OFFSET
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2,1
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COMMENTS
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a(n)-a(n-1) >= 2 due to the fact that n = 10_n, so there is an increment of at least 2. If n can be written as a perfect power m^s, an additional +1 comes to it for the representation of n in each base m.
For instance, for n = 729 we have 729 = 3^6 = 9^3 = 27^2, so there is an additional increment of 3. For n = 1296 we have 1296 = 6^4 = 36^2, so there is an additional increment of 2. For n = 4096 we have 4096 = 2^12 = 4^6 = 8^4 = 16^3= 64^2, so there is an additional increment of 5. (End)
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LINKS
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FORMULA
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a(n) = Sum_{i=1..n-1} floor(n^(1/i));
a(n) = n - 1 + Sum_{i=1..floor(log_2(n))} floor(n^(1/i) - 1);
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EXAMPLE
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5 = 101_2 = 12_3 = 11_4 = 10_5. Thus a(5) = 3+2+2+2 = 9.
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MAPLE
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A043000 := proc(n) add( nops(convert(n, base, b)), b=2..n) ; end proc: # R. J. Mathar, Jun 04 2011
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MATHEMATICA
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Table[Total[IntegerLength[n, Range[2, n]]], {n, 2, 60}] (* Harvey P. Dale, Apr 23 2019 *)
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PROG
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(Magma) [&+[Floor(Log(i, i*n)):k in [2..n]]:n in [1..70]]; // Marius A. Burtea, Nov 13 2019
(Python)
def count(n, b):
c = 0
while n > 0:
n, c = n//b, c+1
return c
n = 0
while n < 50:
n = n+1
a, b = 0, 1
while b < n:
b = b+1
a = a + count(n, b)
(PARI) a(n) = {2*n-2+sum(i=2, logint(n, 2), sqrtnint(n, i)-1)} \\ David A. Corneth, Dec 31 2019
(PARI) first(n) = my(res = vector(n)); res[1] = 2; for(i = 2, n, inc = numdiv(gcd(factor(i+1)[, 2]))+1; res[i] = res[i-1]+inc); res \\ David A. Corneth, Dec 31 2019
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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