A259918 - OEIS

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A259918

Friendly numbers that are smallest in their clubs, ordered by the second-smallest member of the clubs.

6, 30, 80, 40, 12, 84, 66, 78, 102, 114, 240, 138, 120, 150, 174, 135, 186, 864, 222, 246, 60, 258, 282, 560, 318, 330, 354, 366, 720, 390, 402, 426, 360, 438, 880, 474, 498, 510, 440, 534, 132, 1040, 570, 582, 606, 618, 520, 924, 642, 654, 678, 690, 540, 726

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Subsequence of A259917 (see that entry).

LINKS

Table of n, a(n) for n=1..54.

Wikipedia, Friendly number.

PROG

(PARI) known=List(); for(i=1, 10^5, a=sigma(i)/i; match=0; for(j=1, #known, if(known[j][1]==a, match=j; break())); if(match, old=known[match][2]; if(old, print1(old, ", "); known[match]=[a, 0]), listput(known, [a, i])))

CROSSREFS

Cf. A259917, A050973, A095301, A014567.

Sequence in context: A038039 A258903 A050972 * A002444 A152788 A055112

Adjacent sequences: A259915 A259916 A259917 * A259919 A259920 A259921

KEYWORD

nonn

AUTHOR

Jeppe Stig Nielsen, Jul 08 2015

STATUS

approved