A081869 a(1)=2; for n>1, a(n)=2*a(n-1)-1 if that number is composite, a(n)=a(n-1)+1 otherwise.

2, 3, 4, 5, 9, 10, 11, 21, 22, 23, 45, 46, 91, 92, 183, 365, 729, 1457, 2913, 5825, 11649, 11650, 23299, 46597, 93193, 186385, 186386, 372771, 745541, 1491081, 2982161, 5964321, 5964322, 11928643, 23857285, 47714569, 95429137, 95429138, 190858275

Offset

1,1

Links

Table of n, a(n) for n=1..39.

Formula

a(n)=s(n)*2^c(n) where c(n) is an integer sequence and s(n) converges to 1.422004961641565758470595....

Crossrefs

Sequence in context: A303600 A194410 A361125 * A246397 A015837 A262511

Adjacent sequences: A081866 A081867 A081868 * A081870 A081871 A081872

Keyword

nonn

Author

Benoit Cloitre, Apr 12 2003

Status

approved