A185013 - OEIS

A185013

Characteristic function of {3}.

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

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OFFSET

0,1

COMMENTS

Number of connected 2-regular (simple) graphs with girth exactly 3.

LINKS

Table of n, a(n) for n=0..85.

J. S. Kimberley, Index of sequences counting connected k-regular simple graphs with girth exactly g

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

FORMULA

a(n) = A179184(n) - A185114(n).

a(n) = [n = 3], where [ ] is the Iverson bracket. - Wesley Ivan Hurt, Dec 13 2013

MAPLE

A185013:=n->1-abs(signum(3-n)); seq(A185013(n), n=0..100); # Wesley Ivan Hurt, Dec 13 2013

MATHEMATICA

Table[KroneckerDelta[n, 3], {n, 0, 100}] (* Wesley Ivan Hurt, Dec 13 2013 *)

PROG

(PARI) A185013(n)=n==3 \\ M. F. Hasler, Oct 30 2019

(Python)

def A185013(n): return int(n==3) # Chai Wah Wu, Feb 04 2022

CROSSREFS

The Euler transformation of this sequence is A079978.

Characteristic function of {g}: A000007 (g=0), A063524 (g=1), A185012 (g=2), this sequence (g=3), A185014 (g=4), A185015 (g=5), A185016 (g=6), A185017 (g=7).

Sequence in context: A304577 A194670 A130543 * A346459 A193243 A281302

Adjacent sequences: A185010 A185011 A185012 * A185014 A185015 A185016

KEYWORD

nonn,easy

AUTHOR

Jason Kimberley, Oct 11 2011

STATUS

approved