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Search: id:A002460
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| A002460 |
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Nearest integer to exponential integral of n.
(Formerly M1378 N0538)
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+0
1
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| 2, 5, 10, 20, 40, 86, 192, 440, 1038, 2492, 6071, 14960, 37198, 93193, 234956, 595561, 1516638, 3877904, 9950907, 25615653, 66127186, 171144671, 443966370, 1154115392, 3005950907, 7842940992, 20496497120, 53645118592, 140599195758
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
W. G. Bickley and J. C. P. Miller, Numerical differentiation near the limits of a difference table, Phil. Mag., 33 (1942), 1-12 (plus tables).
A. Fletcher, J. C. P. Miller, L. Rosenhead and L. J. Comrie, An Index of Mathematical Tables. Vols. 1 and 2, 2nd ed., Blackwell, Oxford and Addison-Wesley, Reading, MA, 1962, Vol. 1, p. 267.
J. W. L. Glaisher, Phil. Trans. Royal Society, 160 (1870), 367-388.
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FORMULA
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Ei(x) = \int_{-\infty}^x e^t/t dt.
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PROGRAM
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(PARI) a(n)=round(-eint1(-n))
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CROSSREFS
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Sequence in context: A084215 A024810 A049938 this_sequence A006836 A129847 A051109
Adjacent sequences: A002457 A002458 A002459 this_sequence A002461 A002462 A002463
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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