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 A125236 Numbers n for which the absolute value of the abundance of n^2 is a prime number. 4
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified February 7 12:18 EST 2023. Contains 360116 sequences. (Running on oeis4.)