login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A207338 Triangle read by rows in which row n lists the prime factors of n with repetition, with a(1) = 1, but with the primes of the form 4k + 1 multiplied by -1. 2

%I #22 Apr 16 2012 14:09:51

%S 1,2,3,2,2,-5,2,3,7,2,2,2,3,3,2,-5,11,2,2,3,-13,2,7,3,-5,2,2,2,2,-17,

%T 2,3,3,19,2,2,-5,3,7,2,11,23,2,2,2,3,-5,-5,2,-13,3,3,3,2,2,7,-29,2,3,

%U -5,31,2,2,2,2,2,3,11,2,-17,-5,7,2,2,3,3,-37

%N Triangle read by rows in which row n lists the prime factors of n with repetition, with a(1) = 1, but with the primes of the form 4k + 1 multiplied by -1.

%C The row products of triangle give A209662. Also the row products of triangle divided by n give A209661. The mentioned sequences are related to an infinite series which is equal to pi, due to Leonhard Euler.

%e Written as a triangle begins:

%e 1;

%e 2;

%e 3;

%e 2, 2;

%e -5;

%e 2, 3;

%e 7;

%e 2, 2, 2;

%e 3, 3;

%e 2, -5;

%e 11;

%e 2, 2, 3;

%e -13;

%e 2, 7;

%e 3, -5;

%e 2, 2, 2, 2;

%Y Absolute values give A027746.

%Y Cf. A002144, A002145, A209661, A209662.

%K sign,tabf

%O 1,2

%A _Omar E. Pol_, Apr 15 2012

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)