A124809 Numbers of the form (square + 1) that are not squarefree.

50, 325, 1025, 1445, 1682, 1850, 3250, 4625, 4901, 6725, 8650, 9802, 11450, 13690, 13925, 17425, 20450, 24650, 28225, 33125, 37250, 42850, 47525, 53825, 57122, 59050, 63002, 66050, 71825, 79525, 85850, 94250, 101125, 106930, 110225, 117650

Offset: 1

Author

Reinhard Zumkeller, Nov 08 2006

Keywords

• nonn

Comments

The sequence is infinite (see comment in A049532). - Emmanuel Vantieghem, Oct 25 2016

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002522, A013929, A049532, A069987.

Programs

Magma

[n^2+1: n in [1..500]| not IsSquarefree(n^2+1)]; // Vincenzo Librandi, Oct 26 2016

Mathematica

Select[Range[400]^2+1,!SquareFreeQ[#]&] (* Harvey P. Dale, Sep 15 2016 *)

PARI

is(n)=issquare(n-1) && !issquarefree(n) \\ Charles R Greathouse IV, Nov 05 2017

Formula

a(n) = A049532(n)^2 + 1.