A000038 Twice A000007.

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

Author

N. J. A. Sloane

Keywords

• easy
• nonn
• mult

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.

Crossrefs

Cf. A007395, A000007.

Programs

Haskell

a000038 n = 2 * a000007 n -- James Spahlinger, Oct 08 2012

Mathematica

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

PARI

a(n)=if(n,0,2) \\ Charles R Greathouse IV, Oct 09 2012

Formula

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