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A228115 First differences of A227693. 5
3, 21, 143, 1061, 8366, 68932, 585881, 5094722, 45074595, 404185377, 3663479699, 33498077106, 308548877876, 2859703657128, 26646019345842, 249434445759050, 2344494354096166, 22116172789221197, 209301155352811190, 1986521422431963549, 18904049485198437478, 180323870540071281301, 1723847795281971132487, 16512536418951055856540, 158463448213030472998711 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence gives a good approximation of the number of primes with n digits (A006879); see (A228116).

REFERENCES

John H. Conway and R. K. Guy, The Book of Numbers, Copernicus, an imprint of Springer-Verlag, NY, 1996, page 144.

LINKS

Vladimir Pletser, Table of n, a(n) for n = 1..500

Eric Weisstein's World of Mathematics, Fibonacci Polynomial.

FORMULA

a(n)= A227693(n)- A227693(n-1)

EXAMPLE

For n =1, A227693(1)- A227693(0) =4-1=3, where A227693(1)= round((F[3]( 1.016825…))^2)=4 with F[3](x) = x^2+1 and A227693(0)= round(F[1](x)) =1 with F[1](x)=1

CROSSREFS

Cf. A006879, A228111 - A228116

Sequence in context: A337467 A318041 A054419 * A033888 A141492 A243397

Adjacent sequences:  A228112 A228113 A228114 * A228116 A228117 A228118

KEYWORD

nonn

AUTHOR

Vladimir Pletser, Aug 10 2013

STATUS

approved

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Last modified August 7 22:13 EDT 2022. Contains 355995 sequences. (Running on oeis4.)