A194578 Numbers n such that the sum of the first k divisors of n^2+1 is equal to n for some k.

1, 3, 43, 68, 93, 228, 612, 1903, 32292, 44868, 252072, 36564198, 55862807, 134735264

Offset: 1

Author

Michel Lagneau, Aug 29 2011

Keywords

• nonn

Comments

No further at least up to 10^7.

No other terms up to 10^8. - Michel Marcus, Jan 17 2014

a(15) > 2.5*10^8. - Giovanni Resta, Apr 14 2017

Examples

			The divisors of 43^2 + 1 are {1, 2, 5, 10, 25, 37, 50, 74, 185, 370, 925, 1850} and 1+2+5+10 + 25 = 43, hence 43 is in the list.
		

Crossrefs

Cf. A185584.

Programs

Mathematica

Select[Range[10000000], MemberQ[Accumulate[Divisors[#^2+1]], #]&]

Extensions

a(12)-a(13) from Michel Marcus, Jan 17 2014

a(14) from Giovanni Resta, Apr 14 2017