# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a182142 Showing 1-1 of 1 %I A182142 #28 Sep 13 2019 21:16:55 %S A182142 4,3,2,12,10,8,4,2,120,7,56,78,8,2,2,672,32,16,4,2,532,152,136,8,68, %T A182142 31,992,128,8,64,32,16,4,8,128,32,8,2,43648,2528,32,4,2,523776,32, %U A182142 2272,32,32,127,16256,32,32,4,536,8,32,8,52,16,32,41044,64 %N A182142 Abundance d = sigma(N) - 2*N = A033880(N) of numbers N = A153501(n), i.e., N has d > 0 as divisor. %C A182142 It is conjectured that only powers of 2 can occur more than once. %C A182142 Thanks to _Amiram Eldar_, reference to A181595 in the definition has been corrected to A153501 (which does include triperfect numbers, as required here, in contrast to A181595 where these are excluded). - _M. F. Hasler_, Sep 11 2019 %H A182142 M. F. Hasler, Table of n, a(n) for n = 1..200, Sep 11 2019 %F A182142 Equals A033880 o A153501. %o A182142 (PARI) f182142(n)={my(d=sigma(n)-2*n); d>0 && !(n%d) && return(d)} /* Note: This is A033880(n)*is_A153501(n), neither A182142 nor is_A182142. */ %o A182142 for(n=1,1e6,(t=f182142(n))&&print1(t",")) %Y A182142 Cf. A033880, A153501, A181595. %K A182142 nonn %O A182142 1,1 %A A182142 _M. F. Hasler_, Apr 14 2012 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE