A160966 Starting from a(1)=2, a(n) = A028260(1+a(n-1)) if n is even, a(n) = A026424(a(n-1)) if n is odd.

2, 6, 11, 25, 45, 94, 176, 361, 700, 1405, 2752, 5533, 10964, 22011, 43839, 87868, 175557, 351746, 703243, 1407705, 2814709, 5631461, 11261009, 22524901, 45044446, 90091251, 180165450, 360333977, 720640449, 1441293048, 2882532607, 5765114161, 11530179777

Offset

1,1

Comments

If a(1) were set to 3, the equivalent sequence would start 3, 9, 17, 38, 71, 146, 279,...

Alternatively starting from a(1)=4 we get 4, 10, 18, 39, 72, 150,..

Links

Chai Wah Wu, Table of n, a(n) for n = 1..42

Example

a(2) = 6, the second integer containing an even number of prime factors.
a(3) = 11, the sixth integer containing an odd number of primes.

Crossrefs

Cf. A026424, A028260, A141436.

Sequence in context: A067605 A072986 A079047 * A052326 A079118 A211054

Adjacent sequences: A160963 A160964 A160965 * A160967 A160968 A160969

Keyword

nonn

Author

Daniel Tisdale, May 31 2009

Extensions

Definition clarified, sequence extended beyond 25 by R. J. Mathar, May 31 2010

a(15)-a(31) from Donovan Johnson, Jul 02 2010

a(32)-a(33) from Chai Wah Wu, Jan 22 2026

Status

approved