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!)
A145215 a(n) is the minimal prime of the form 4k+1 for which s=A008784(n) is the minimal positive integer such that s*a(n)-floor(sqrt(s*a(n)))^2 is a square. 3
5, 41, 353, 1237, 2749, 3037, 10369, 6569, 27253, 38561, 14897, 33289, 27917, 171629, 143513, 76081, 37649, 373273, 399181, 63029, 133157, 637601, 425197, 94261, 499321, 910853, 229849, 149837 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
See the conjecture in the comment at A145047. In addition, I conjecture that for every such s there exist infinitely many primes of the form 4k+1.
LINKS
PROG
(PARI) f(s)=forprime(p=2, , if(p%4>1 || !issquare(s*p-sqrtint(s*p)^2), next); for(i=1, s-1, if(issquare(i*p-sqrtint(i*p)^2), next(2))); return(p))
S=select(n->if(n%2==0, if(n%4, n/=2, return(0))); n==1||vecmax(factor(n)[, 1]%4)==1, vector(150, i, i));
apply(f, S) \\ Charles R Greathouse IV, Feb 07 2013
CROSSREFS
Sequence in context: A202249 A067381 A155612 * A083884 A156153 A026000
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Oct 05 2008
EXTENSIONS
a(22) corrected by Charles R Greathouse IV, Feb 07 2013
STATUS
approved

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 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)