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!)
A264858 Integers k such that A007504(k) + 1 is a square. 1
0, 17, 539, 652, 6420, 350857847 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Integers k such that the sum of the first k primes + 1 is a square.
Integers k such that A014284(k+1) is a square.
In A110996, it is commented that a(6) > 250000, if it exists.
a(6) > 50000000, if it exists. - Jon E. Schoenfield, Nov 29 2015
LINKS
EXAMPLE
a(2) = 17 because A007504(17) + 1 = 440 + 1 = 441 is a square.
MATHEMATICA
t = Accumulate[Prime@ Range@ 100000]; Prepend[Select[Range@ 7000, IntegerQ@ Sqrt[t[[#]] + 1] &], 0] (* Michael De Vlieger, Nov 29 2015, after Zak Seidov at A007504 *)
Join[{0}, Position[Accumulate[Prime[Range[6500]]]+1, _?(IntegerQ[Sqrt[ #]]&)]] // Flatten (* Harvey P. Dale, Feb 12 2018 *)
PROG
(PARI) lista(nn) = { print1(0, ", "); s = 1; for(k=1, nn, s += prime(k); if(issquare(s), print1(k, ", ")); ); }
CROSSREFS
Sequence in context: A114063 A214135 A193120 * A112716 A218351 A197395
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Nov 26 2015
EXTENSIONS
a(6) from Jinyuan Wang, Aug 09 2023
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 June 24 19:44 EDT 2024. Contains 373690 sequences. (Running on oeis4.)