A125236 Numbers n for which the absolute value of the abundance of n^2 is a prime number.

3, 5, 6, 7, 9, 10, 11, 14, 15, 17, 18, 22, 24, 26, 28, 29, 30, 31, 33, 34, 35, 44, 47, 50, 56, 58, 61, 65, 66, 67, 68, 69, 71, 72, 74, 75, 80, 85, 91, 94, 96, 97, 100, 101, 102, 104, 116, 118, 120, 121, 124, 125, 127, 131, 134, 136, 139, 144, 148, 149, 152, 164, 166, 170

Offset: 1

Author

Jason G. Wurtzel, Nov 25 2006

Keywords

• nonn

Examples

			n=5: n^2=25, sigma(25)=25+5+1=31, 2*25=50, abundance=-19.
		

Links

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

Crossrefs

Cf. A088005.

Programs

Mathematica

Select[Range[170], PrimeQ[DivisorSigma[1, #^2] - 2*#^2] &] (* Amiram Eldar, Sep 23 2019 *)

PARI

for(n=1,170,if(isprime(abs(sigma(n^2)-2*n^2)),print1(n,","))) \\ Klaus Brockhaus, Nov 25 2006

Extensions

More terms from Klaus Brockhaus, Nov 25 2006