A090340 - OEIS

%I #15 Apr 23 2020 15:28:03

%S -2,-1,-1,-1,0,-2,1,0,-1,-4,4,-6,4,1,0,-9,9,-11,10,-1,-3,-10,14,-1,-5,

%T 6,-2,-18,19,-21,21,-4,-5,7,2,-27,16,5,5,-30,29,-31,28,4,-14,-22,36,

%U -3,2,-8,3,-36,42,-5,3,-9,-9,-28,47,-49,28,20,1,-6,2,-51,46,-5,12,-57,59,-61,34,26,-10,5,0,-61,66,1,-31,-40,69,-8,-23,13

%N Difference between the sums of the prime factors, including multiplicity, of n and those of n + 1.

%C If a(n) = 0 then n is a Ruth-Aaron number. - _Andrew Slattery_, Apr 15 2020

%F a(n) = sopfr(n) - sopfr(n+1), where sopfr = A001414. - _Wesley Ivan Hurt_, Aug 10 2016

%e a(24)=-1 because 24=2*2*2*3, 25=5*5 and (2+2+2+3)-(5+5)=-1.

%Y Cf. A001414 (sopfr), A090341, A090342, A090343.

%Y Ruth-Aaron numbers: A039752.

%K sign

%O 1,1

%A Charles K. Layman (cklayman(AT)juno.com), Nov 25 2003