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A102049 Indices of primes which are denominators of convergents to e. 2
2, 4, 20, 2073, 688812, 23493068282804, 51287550456151700 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The prime denominators of convergents to e form A094008 (so A000040(a(n)) = A094008(n)). Their positions in A007677 (denominators of convergents to e) form A094007, so a(n) = A000720(A007677(A094007(n))).

a(6)-a(7) computed using Kim Walisch's primecount program. - Giovanni Resta, Jun 03 2019

LINKS

Table of n, a(n) for n=1..7.

E. B. Burger, Diophantine Olympics and World Champions: Polynomials and Primes Down Under, Amer. Math. Monthly, 107 (Nov. 2000), 822-829.

J. Sondow, A geometric proof that e is irrational and a new measure of its irrationality, Amer. Math. Monthly 113 (2006) 637-641 (article), 114 (2007) 659 (addendum).

J. Sondow, A geometric proof that e is irrational and a new measure of its irrationality, arXiv:0704.1282 [math.HO], 2007-2010.

J. Sondow and K. Schalm, Which partial sums of the Taylor series for e are convergents to e? (and a link to the primes 2, 5, 13, 37, 463), II, Gems in Experimental Mathematics (T. Amdeberhan, L. A. Medina, and V. H. Moll, eds.), Contemporary Mathematics, vol. 517, Amer. Math. Soc., Providence, RI, 2010; arXiv:0709.0671 [math.NT], 2007-2009.

Eric Weisstein's World of Mathematics, e.

FORMULA

a(n) = A000720(A094008(n)).

EXAMPLE

a(1) = 2 because the first convergent to e with prime denominator is 8/3 and the index of 3 is 2, i.e., 3 is the 2nd prime.

CROSSREFS

Cf. A000040, A000720, A007677, A094007, A094008.

Sequence in context: A087314 A326972 A099179 * A058522 A292534 A122736

Adjacent sequences: A102046 A102047 A102048 * A102050 A102051 A102052

KEYWORD

nonn,more

AUTHOR

Jonathan Sondow, Dec 27 2004

EXTENSIONS

a(6)-a(7) from Giovanni Resta, Jun 03 2019

STATUS

approved

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Last modified December 3 20:26 EST 2022. Contains 358543 sequences. (Running on oeis4.)