A185017 Characteristic function of 7.

0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,1

Comments

Number of connected 2-regular (simple) graphs with girth exactly 7.

The Euler transformation of this sequence is A082784.

Links

Table of n, a(n) for n=0..101.

Index entries for linear recurrences with constant coefficients, signature (1).

Formula

a(n) = A185117(n) - A185118(n).

Mathematica

PadRight[{0, 0, 0, 0, 0, 0, 0, 1}, 100] (* Paolo Xausa, May 07 2026 *)

Prog

(Python)
def A185017(n): return int(n==7) # Chai Wah Wu, Feb 04 2022

Crossrefs

Characteristic function of g: A000007 (g=0), A063524 (g=1), A185012 (g=2), A185013 (g=3), A185014 (g=4), A185015 (g=5), A185016 (g=6), this sequence (g=7).

Cf. A185117, A185118.

Sequence in context: A276404 A277153 A323162 * A359472 A295883 A366124

Adjacent sequences: A185014 A185015 A185016 * A185018 A185019 A185020

Keyword

nonn,easy

Author

Jason Kimberley, Oct 14 2011

Status

approved