cp's OEIS Frontend

A294393 a(n) is the smallest number whose deficiency or abundance is equal to 2*n (or 0 if such a number does not exist), minus the n-th odd number.

%I A294393 #33 Nov 02 2017 05:33:22
%S A294393 5,0,0,0,13,0,0,12,0,0,25,0,87,31,0,0,217,22,0,16,0,0,49,0,11,55,0,32,
%T A294393 27,0,0,22,43,0,73,0,0,637,81,0,75,0,320,28,0,50,313,24,0,103,0,0,109,
%U A294393 0,0,34,0,62,301,24,-1,120,67,0,133,0,128,139,0,0,433,42,23,151,0,0,219,82,0,28,119
%N A294393 a(n) is the smallest number whose deficiency or abundance is equal to 2*n (or 0 if such a number does not exist), minus the n-th odd number.
%C A294393 Note that a(60) = -1.
%F A294393 a(n) = A294386(n) - A005408(n).
%e A294393 --------------------------------------
%e A294393 n    A294386(n) - A005408(n)  =  a(n)
%e A294393 --------------------------------------
%e A294393 0        6            1           5
%e A294393 1        3            3           0
%e A294393 2        5            5           0
%e A294393 3        7            7           0
%e A294393 4       22            9          13
%e A294393 ...
%o A294393 (PARI) f(n) = abs(2*n-sigma(n));
%o A294393 a(n) = my(k=1); while(f(k) != 2*n, k++); k - (2*n+1); \\ _Michel Marcus_, Oct 31 2017
%Y A294393 Cf. A000203, A000396, A005100, A005101, A033879, A033880, A234285, A234286, A294347, A294386.
%K A294393 sign
%O A294393 0,1
%A A294393 _Omar E. Pol_, Oct 30 2017