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A064730 Numbers whose sum of nonunitary divisors and sum of unitary divisors are both positive squares. 5
15012, 124956, 128412, 135972, 186732, 219520, 241812, 377892, 414180, 420660, 447876, 453060, 453492, 497772, 504036, 515052, 523044, 528876, 544212, 658560, 776412, 826956, 1009792, 1020060, 1135836, 1191132, 1425060, 1467180, 1511892 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..750

PROG

(PARI) {usigma(n, s=1, fac, i) = fac=factor(n); for(i=1, matsize(fac)[1], s=s*(1+fac[i, 1]^fac[i, 2])); return(s); } nu(n) = sigma(n)-usigma(n); for(n=1, 10^8, if(nu(n)>0 && issquare(nu(n)) && issquare(usigma(n)), print1(n, ", ")))

(PARI) usigma(n)= { local(f, s=1); f=factor(n); for(i=1, matsize(f)[1], s*=1 + f[i, 1]^f[i, 2]); return(s) } { n=0; for (m = 1, 10^9, u=usigma(m); nu=sigma(m) - u; if (nu>0 && issquare(nu) && issquare(u), write("b064730.txt", n++, " ", m); if (n==750, break)) ) } \\ Harry J. Smith, Sep 24 2009

CROSSREFS

Cf. A034448, A048146.

Sequence in context: A178929 A145275 A234654 * A081635 A165614 A104875

Adjacent sequences:  A064727 A064728 A064729 * A064731 A064732 A064733

KEYWORD

nonn

AUTHOR

Jason Earls, Oct 17 2001

STATUS

approved

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Last modified January 20 14:17 EST 2021. Contains 340302 sequences. (Running on oeis4.)