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A236372 Terms of A050973 that give minimum record values for A050973(k)/A050972(k). 1
28, 200, 936, 7856640, 12103000, 8004519424 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

LINKS

Table of n, a(n) for n=1..6.

Eric Weisstein's World of Mathematics, Friendly Pair.

EXAMPLE

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

PROG

(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, ", "); ); ); }

CROSSREFS

Cf. A050972, A050973, A236355.

Sequence in context: A184933 A233039 A246902 * A159542 A244944 A155466

Adjacent sequences:  A236369 A236370 A236371 * A236373 A236374 A236375

KEYWORD

nonn,more,bref

AUTHOR

Michel Marcus, Jan 24 2014

EXTENSIONS

a(6) from Michel Marcus, Feb 08 2014

STATUS

approved

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Last modified August 15 01:47 EDT 2020. Contains 336485 sequences. (Running on oeis4.)