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

0,2

Links

Table of n, a(n) for n=0..40.

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

Prog

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

Crossrefs

Cf. A170803.

Sequence in context: A179018 A352476 A205476 * A013984 A107479 A117761

Adjacent sequences: A170802 A170803 A170804 * A170806 A170807 A170808

Keyword

nonn

Author

N. J. A. Sloane, Dec 12 2009

Status

approved