A155721 Positions of parity change in A033035.

4, 20, 84, 340, 1364, 5460, 21844, 87380, 349524, 1398100, 5592404, 22369620, 89478484, 357913940, 1431655764, 5726623060, 22906492244, 91625968980, 366503875924, 1466015503700, 5864062014804, 23456248059220, 93824992236884

Offset

1,1

Comments

Numbers n such that A033035(n)=(7/8)*(9^n - 1)=7*A002452(n).

Links

Table of n, a(n) for n=1..23.

Formula

a(n=1,2..)=(4/3)*(4^n-1)=A080674(n).

a(n) = 5*a(n-1) - 4*a(n-2) for n > 2. G.f.: 4*x/((x - 1)*(4*x - 1)). - Chai Wah Wu, Aug 30 2019

Example

A033035(n=1..4) all are odd, then A033035(n=5..20) all are even, then A033035(n=21..84) all are odd, then A033035(n=85..340) all are even, etc.

Crossrefs

A002452, A033035, A080674.

Sequence in context: A003489 A167682 A246574 * A084240 A080674 A246936

Adjacent sequences: A155718 A155719 A155720 * A155722 A155723 A155724

Keyword

nonn

Author

Zak Seidov, Jan 25 2009

Status

approved