A114082 sigma(n) plus the n-th prime gives a square.

3, 6, 7, 9, 18, 58, 73, 134, 198, 251, 278, 287, 461, 483, 505, 525, 529, 665, 772, 939, 960, 986, 1291, 1432, 1463, 1629, 2115, 2931, 2991, 3422, 3888, 4159, 4231, 4548, 4715, 6256, 7867, 9148, 9474, 9540, 9958, 10535, 12035, 12081, 12223, 12511

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

sigma(2115)+p(2115)=22201=149^2.

Mathematica

n=0; p=1; seq={}; Do[p = NextPrime[p]; n++; If[IntegerQ @ Sqrt [p + DivisorSigma[1, n]], AppendTo[seq, n]], {10^4}]; seq (* Amiram Eldar, Aug 18 2019 *)

Prog

(PARI) isok(n) = issquare(sigma(n) + prime(n)); \\ Michel Marcus, Jan 11 2014

Crossrefs

Cf. A114081, A114083.

Sequence in context: A191187 A310134 A039591 * A343218 A185339 A189015

Adjacent sequences: A114079 A114080 A114081 * A114083 A114084 A114085

Keyword

nonn

Author

Giovanni Resta, Feb 13 2006

Status

approved