OFFSET
1,1
COMMENTS
Inspired by A243106. In contrast to that sequence, the absolute values are not increasing here.
This can be explained as follows: By comparison of the absolute values among both sequences, after replacing for each term at the other sequence: 8,9 with 0,1 it is obtained the a(n) corresponding here expressed in binary with one or more "leading zeros". This induces the described effect, cf. example. - R. J. Cano, Aug 20 2014
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..1000
EXAMPLE
From R. J. Cano, Aug 20 2014: (Start)
By looking at A243106's b-file for n=28..30:
28 11110911090911090911090908910
29 -88889088909088909088909091090
30 911110911090911090911090908910
After taking the absolute values, making the replacements, and deleting the leading zeros, we obtain:
28 11110111010111010111010100110
29 1000101000101000101011010 (4 leading zeros deleted)
30 111110111010111010111010100110
From where it is noticeable that abs(a(28))>abs(a(29))<abs(a(30)); Now by reading from binary:
abs(a(28))=518762150
abs(a(29))=18108762 (it was negative)
abs(a(30))=1055633062 (End)
PROG
(PARI) a(n, b=2)=sum(k=1, n, (-1)^isprime(k)*b^k)
CROSSREFS
KEYWORD
sign
AUTHOR
M. F. Hasler, Aug 20 2014
STATUS
approved