A170805 a(n) = A170803(n-1) + 2, with a(0) = 1, a(1) = 2.

1, 2, 3, 5, 8, 12, 20, 29, 45, 72, 104, 168, 249, 377, 620, 876, 1388, 2117, 3141, 5189, 7376, 11472, 18033, 26225, 42609, 62292, 95060, 154109, 219645, 350717, 527864, 790008, 1314296, 1845737, 2894313, 4488636, 6585788, 10780092, 15563061, 23951669, 38300576

Offset: 0

Author

N. J. A. Sloane, Dec 12 2009

Keywords

• nonn

Links

• Boris Alexeev, Minimal DFAs for testing divisibility, arXiv:cs/0309052 [cs.CC], 2003.

Crossrefs

Cf. A170803.

Programs

Python

from sympy import integer_log
def A170805(n): return n+1 if n<2 else ((a:=1<>1) if 6**(k:=integer_log(m:=3**(n-2),6)[0])<<1>1)+(1<Chai Wah Wu, Feb 05 2025