A000038 Twice A000007. (Formerly M0004)

2, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,1

Comments

Multiplicative with a(p^e) = 0. - Mitch Harris, Jun 09 2005

Also decimal expansion of 1/5, with keyword cons. - Wolfdieter Lang, Jan 19 2023

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

James Spahlinger, Table of n, a(n) for n = 0..10000

Norman L. de Forest, The Square Root of 4 to a Million Places, Project Gutenberg EBook 3651, 2003.

Daniele A. Gewurz and Francesca Merola, Sequences realized as Parker vectors of oligomorphic permutation groups, J. Integer Seqs., Vol. 6, 2003.

Chai Wah Wu, Can machine learning identify interesting mathematics? An exploration using empirically observed laws, arXiv:1805.07431 [cs.LG], 2018.

Dominika Závacká, Cristina Dalfó, and Miquel Angel Fiol, Integer sequences from k-iterated line digraphs, CEUR: Proc. 24th Conf. Info. Tech. - Appl. and Theory (ITAT 2024) Vol 3792, 156-161. See p. 161, Table 2. See p. 6.

Formula

a(n) = 2*A000007(n) = (-1)^A000040(n) + 1. - Juri-Stepan Gerasimov, Oct 29 2009

Mathematica

PadRight[{2}, 104] (* or *)
Array[(-1)^Prime@ # + 1 &, 105] (* Michael De Vlieger, Aug 15 2018 *)

Prog

(Haskell)
a000038 n = 2 * a000007 n -- James Spahlinger, Oct 08 2012
(PARI) a(n)=if(n, 0, 2) \\ Charles R Greathouse IV, Oct 09 2012

Crossrefs

Cf. A007395, A000007.

Sequence in context: A340851 A130779 A130706 * A335462 A353349 A349399

Adjacent sequences: A000035 A000036 A000037 * A000039 A000040 A000041

Keyword

easy,nonn,mult

Author

N. J. A. Sloane

Status

approved