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A001467
Denominators of an expansion for Pi.
(Formerly M4464 N1893)
2
1, 1, 1, 7, -791, -3748629, 151648960887729, -1323497544567561138595307148089, 41444465282455711991644958522615049159671653083333293470875123
OFFSET
0,4
REFERENCES
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Mohammad K. Azarian, An Expression for Pi, Problem #870, College Mathematics Journal, Vol. 39, No. 1, January 2008, p. 66. Solution appeared in Vol. 40, No. 1, January 2009, pp. 62-64.
H. E. Salzer, The approximation of numbers as sums of reciprocals, Amer. Math. Monthly, 54 (1947), 135-142.
FORMULA
Numerators are 1.
EXAMPLE
a(4) = -791 since Pi - (1/1) - (1/1) - (1/1) - (1/7) = -0.001264489... is closer to 1/(-791) = -0.001264222... than to 1/(-790) = -0.0012658228...
PROG
(PARI) x=Pi; for(k=0, 8, if(x<1, d=round(1/x), d=1); x=x-1/d; print(d, ", ")) \\ Jaume Oliver Lafont, Feb 21 2009
CROSSREFS
KEYWORD
sign,frac
EXTENSIONS
Edited by Henry Bottomley, Jul 30 2002
STATUS
approved