A218709 a(n) is smallest number such that a(n)^2 + 1 is divisible by 13^n.

0, 5, 70, 239, 239, 143044, 1999509, 6826318, 6826318, 822557039, 52199939826, 603633907222, 11356596271444, 11356596271444, 1828607235824962, 13920898306972194, 13920898306972194, 2675587335039691558, 49226908181248336040, 513050126578538629605

Offset: 0

Author

Michel Lagneau, Nov 04 2012

Keywords

• nonn

Examples

			a(4) = 239 because 239^2+1 = 2*13^4.
		

Crossrefs

Cf. A002522, A049532, A034939.

Programs

Mathematica

b=5;n13=13;jo=Join[{0,b},Table[n13=13*n13;b=PowerMod[b,13,n13];b=Min[b,n13-b],{99}]]