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

1,1

Links

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A088005.

Sequence in context: A352873 A047984 A288513 * A137624 A238246 A330998

Adjacent sequences: A125233 A125234 A125235 * A125237 A125238 A125239

Keyword

nonn

Author

Jason G. Wurtzel, Nov 25 2006

Extensions

More terms from Klaus Brockhaus, Nov 25 2006

Status

approved