cp's OEIS Frontend

A176717 Numbers n such that sum of digits of all distinct prime factors of n-th semiprime = sum of digits of all distinct prime factors of (n+1)-th semiprime.

%I A176717 #8 Feb 02 2015 05:29:36
%S A176717 13,15,16,20,79,91,111,116,117,119,125,131,205,215,225,250,276,282,
%T A176717 284,298,303,313,332,340,362,364,446,501,523,554,562,686,720,728,759,
%U A176717 796,798,830,877,904,923,925,953,962,978,986,988,992,1007,1056,1097,1117
%N A176717 Numbers n such that sum of digits of all distinct prime factors of n-th semiprime = sum of digits of all distinct prime factors of (n+1)-th semiprime.
%e A176717 a(1)=2 because 1st semiprime = 2*2 and 2=2; a(2)=5 because 2nd semiprime=2*3 and 2<3.
%p A176717 A007953 := proc(n) add(d,d=convert(n,base,10)) ; end proc: A176707 := proc(n) local p; p := numtheory[factorset](A001358(n)) ; add( A007953(d),d=p) ; end proc: isA176717 := proc(n) A176707(n) = A176707(n+1) ; end proc: for n from 1 to 1200 do if isA176717(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Apr 26 2010
%Y A176717 Cf. A095402, A176707.
%K A176717 nonn,base
%O A176717 1,1
%A A176717 _Juri-Stepan Gerasimov_, Apr 24 2010
%E A176717 Corrected (13 inserted, 20 inserted, 34 and 55 removed) and extended beyond 91 by _R. J. Mathar_, Apr 26 2010