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

Offset: 1

Author

Jeppe Stig Nielsen, Jul 08 2015

Keywords

• nonn

Comments

Subsequence of A259917 (see that entry).

Links

• Wikipedia, Friendly number.

Crossrefs

Cf. A259917, A050973, A095301, A014567.

Programs

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])))