A071293 a(0)=1, a(n) is the smallest integer > a(n-1) such that the continued fraction for 1/a(0)+1/a(1)+1/a(2)+...+1/a(n) contains exactly 2^n elements.

1, 2, 5, 11, 573, 71081, 506860777

Offset

0,2

Links

Table of n, a(n) for n=0..6.

Example

The continued fraction for 1/a(0)+1/a(1)+1/5 = 1+1/2+1/5 is {1, 1, 2, 3} which contains 2^2 elements. 5 is the smallest integer > 2 with this property, hence a(2)=5.

Prog

(PARI) s=1; t=1; for(n=1, 5, s=s+1/t; while(abs(2^n-length(contfrac(s+1/t)))>0, t++); print1(t, ", "))

Crossrefs

Sequence in context: A069504 A158997 A101828 * A234572 A341804 A109623

Adjacent sequences: A071290 A071291 A071292 * A071294 A071295 A071296

Keyword

hard,nonn

Author

Benoit Cloitre, Jun 11 2002

Extensions

One more term from Michel ten Voorde Jun 13 2003

Status

approved