A067465 Numbers k such that sigma(k^2+1) is a perfect square.

0, 13, 64, 67, 189, 344, 900, 2499, 3028, 4253, 5257, 6277, 9075, 11516, 12544, 18739, 18925, 47018, 49011, 62355, 72981, 112061, 125011, 125653, 152765, 167820, 168317, 174724, 179040, 225492, 240597, 251568, 261163, 302128, 302812, 345283

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..300

Mathematica

Select[Range[0, 400000], IntegerQ[Sqrt[DivisorSigma[1, #^2+1]]]&] (* Harvey P. Dale, May 14 2018 *)

Prog

(PARI) for(n=0, 500000, if(issquare(sigma(n^2+1)), print1(n, ", ")))

Crossrefs

Cf. A000203, A000290, A002522, A006532, A193433.

Sequence in context: A265038 A051878 A092653 * A166605 A054477 A169883

Adjacent sequences: A067462 A067463 A067464 * A067466 A067467 A067468

Keyword

nonn

Author

Benoit Cloitre, Feb 23 2002

Extensions

More terms from Rick L. Shepherd, Apr 16 2002

Status

approved