A070154 Number of terms in the simple continued fraction expansion of Sum_{k=0..n}(-1)^k/(2k+1), the Leibniz-Gregory series for Pi/4.

1, 3, 4, 9, 5, 9, 14, 10, 10, 19, 16, 21, 22, 22, 24, 20, 19, 24, 28, 28, 29, 30, 39, 31, 44, 40, 44, 33, 41, 47, 44, 48, 54, 48, 60, 49, 63, 51, 65, 72, 64, 70, 78, 64, 79, 77, 74, 87, 75, 86, 82, 94, 88, 106, 106, 94, 104, 108, 87, 107, 86, 106, 98, 110, 115, 110, 105, 115

Offset

0,2

Comments

Pi/4 = Sum_{k=>0} (-1)^k/(2k+1).

Links

Amiram Eldar, Table of n, a(n) for n = 0..10000

Formula

Limit_{n -> infinity} a(n)/n = C = 1.6...

Example

The simple continued fraction for Sum(k=0,10,(-1)^k/(2k+1)) is [0, 1, 4, 4, 1, 3, 54, 1, 2, 1, 1, 4, 11, 1, 2, 2] which contains 16 elements, hence a(10)=16.

Mathematica

lcf[f_] := Length[ContinuedFraction[f]]; lcf /@ Accumulate[Table[(-1)^k/(2*k + 1), {k, 0, 100}]] (* Amiram Eldar, Apr 29 2022 *)

Prog

(PARI) for(n=1, 100, print1( length(contfrac(sum(i=0, n, (-1)^i/(2*i+1)))), ", "))

Crossrefs

Cf. A003881, A007509, A055573, A069880, A069887.

Sequence in context: A276521 A247567 A271529 * A331025 A330403 A183211

Adjacent sequences: A070151 A070152 A070153 * A070155 A070156 A070157

Keyword

easy,nonn

Author

Benoit Cloitre, May 06 2002

Extensions

Offset changed to 0 and a(0) inserted by Amiram Eldar, Apr 29 2022

Status

approved