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A087719 Least number m such that the number of numbers k <= m with k > spf(k)^n exceeds the number of numbers with k <= spf(k)^n. 1
15, 27, 57, 135, 345, 927, 2577, 7335, 21225, 62127, 183297, 543735, 1618905, 4832127, 14447217, 43243335, 129533385, 388206927, 1163834337, 3489930135, 10466644665, 31393642527, 94168344657, 282479868135 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

m<a(n): #{k: k>spf(k)^n & 1<=k<=m} <= m/2;

m>=a(n): #{k: k>spf(k)^n & 1<=k<=m} > m/2.

LINKS

Table of n, a(n) for n=1..24.

FORMULA

Numbers so far satisfy a(n) = 3^n + 3*2^n + 6. - Ralf Stephan, May 10 2004

Empirical G.f.: 3*x*(5-21*x+20*x^2)/(1-x)/(1-2*x)/(1-3*x)). [Colin Barker, Feb 22 2012]

CROSSREFS

Cf. A088382, A088382, A088380, A088381, A000430, A080257.

Sequence in context: A110978 A274433 A227804 * A174216 A249874 A116070

Adjacent sequences:  A087716 A087717 A087718 * A087720 A087721 A087722

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Sep 29 2003

EXTENSIONS

a(14)-a(24) from Giovanni Resta, May 23 2013

STATUS

approved

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Last modified March 22 17:25 EDT 2019. Contains 321422 sequences. (Running on oeis4.)