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A222642
Integer nearest to (Li(n) - Li(sqrt(n))), where Li(x) = integral(0..x, dt/log(t)).
1
1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 18, 19, 19
OFFSET
2,2
COMMENTS
Challenge: find the smallest n for which pi(n) < a(n), where pi(n) is the prime counting function.
LINKS
Arkadiusz Wesolowski, Table of n, a(n) for n = 2..10000
MATHEMATICA
Table[Round[LogIntegral[n] - LogIntegral@Sqrt[n]], {n, 2, 74}]
PROG
(PARI) a(n)=round(real(eint1(-log(n)/2)-eint1(-log(n)))) \\ Charles R Greathouse IV, Feb 27 2013
CROSSREFS
Cf. A047743.
Sequence in context: A137214 A284726 A319951 * A081832 A034887 A192543
KEYWORD
nonn
AUTHOR
STATUS
approved