cp's OEIS Frontend

A210936 Sum of prime factors of prime(n)-1 (counted with multiplicity).

%I A210936 #21 May 25 2022 08:54:40
%S A210936 0,2,4,5,7,7,8,8,13,11,10,10,11,12,25,17,31,12,16,14,12,18,43,17,13,
%T A210936 14,22,55,13,15,15,20,23,28,41,15,20,14,85,47,91,15,26,15,18,19,17,42,
%U A210936 115,26,35,26,16,17,16,133,71,16,30,18,52,77,25,38,22,83
%N A210936 Sum of prime factors of prime(n)-1 (counted with multiplicity).
%C A210936 From an idea of _Michael B. Porter_.
%H A210936 Paolo P. Lava, <a href="/A210936/b210936.txt">Table of n, a(n) for n = 1..10000</a>
%F A210936 a(n) = A001414(A006093(n)). - _Michel Marcus_, Oct 05 2013
%e A210936 prime(10) = 29, and 29-1 = 28 = 2*2*7, so a(10) = 2+2+7 = 11.
%p A210936 with(numtheory);
%p A210936 P:=proc(i)
%p A210936 local a,k,n;
%p A210936 for n from 1 to i do
%p A210936   a:=ifactors(ithprime(n)-1)[2]; print(add(a[k][1]*a[k][2],k=1..nops(a)));
%p A210936 od; end:
%p A210936 # alternative
%p A210936 A210936 := proc(n)
%p A210936         local p,pplus,f ;
%p A210936         p := ithprime(n) ;
%p A210936         pplus := ifactors(p-1)[2] ;
%p A210936         add(op(1,f)*op(2,f),f=pplus) ;
%p A210936 end proc:
%p A210936 seq(A210936(n),n=1..300) ; # _R. J. Mathar_, May 25 2022
%Y A210936 Cf. A023508, A023514, A210934
%K A210936 nonn
%O A210936 1,2
%A A210936 _Paolo P. Lava_, Mar 30 2012