A236372 Terms of A050973 that give minimum record values for A050973(k)/A050972(k).

28, 200, 936, 7856640, 12103000, 8004519424

Offset: 1

Author

Michel Marcus, Jan 24 2014

Keywords

• nonn
• more

Comments

The corresponding terms in A050972 are: 6, 80, 864, 7344000, 11804800, 7908221230.

Note that from n=1 to 4 sigma(a(n))/a(n) is increasing, but decreasing for n=5 and 6. Is this going on afterwards? - Michel Marcus, Feb 08 2014

Examples

			28/6 > 200/80 > 936/864 > 7856640/7344000 > 12103000/11804800 > ...
		

Links

• Eric Weisstein's World of Mathematics, Friendly Pair.

Crossrefs

Cf. A050972, A050973, A236355.

Programs

PARI

isrmin(i, rmin) = {si = sigma(i); if (gcd(si, i) == 1, return (0)); s = si/i; forstep (j=i-1, 1+i\rmin, -1, if ((sigma(j)/j) == s, if ((newr = i/j) < rmin, return (newr)););); return (0);}
lista(nn) = {rmin = 1000; for (i=1, nn, if ((newr = isrmin(i, rmin)), rmin = newr; print1(i, ", ");););}

Extensions

a(6) from Michel Marcus, Feb 08 2014