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A082912
Least k such that H(k) > 10^n, where H(k) is the harmonic number Sum_{i=1..k} 1/i.
1
2, 12367, 15092688622113788323693563264538101449859497
OFFSET
0,1
COMMENTS
"In 1968 John W. Wrench Jr calculated the exact minimum number of terms needed for the series to sum past 100; that number is 15 092 688 622 113 788 323 693 563 264 538 101 449 859 497. Certainly, he did not add up the terms.
"Imagine a computer doing so and suppose that it takes it 10^-9 seconds to add each new term to the sum and that we set it adding and let it continue doing so indefinitely. The job will have been completed in not less than 3.5 * 10^17 (American) billion years." Havil.
REFERENCES
Julian Havil, Gamma, Exploring Euler's Constant, Princeton University Press, Princeton and Oxford, 2003, page 23.
LINKS
R. Baillie, Fun With Very Large Numbers, arXiv preprint arXiv:1105.3943, 2011
R. P. Boas, Jr. and J. W. Wrench, Jr., Partial sums of the harmonic series, Amer. Math. Monthly, 78 (1971), 864-870.
Eric Weisstein's World of Mathematics, Harmonic Number
FORMULA
H(k) ~= log(k) + Euler's Gamma Constant (A001620) + 1/(2k).
a(n) = A002387(10^n). - Joerg Arndt, Jul 13 2015
MATHEMATICA
f[n_] := Floor[Exp[n - EulerGamma] - 1/2] + 1; Table[ f[10^n], {n, 0, 2}]
CROSSREFS
Sequence in context: A082178 A345396 A287650 * A265013 A083973 A094212
KEYWORD
nonn,bref
AUTHOR
Robert G. Wilson v, Apr 14 2003
STATUS
approved