%I A037916
%S A037916 0,1,1,2,1,11,1,3,2,11,1,21,1,11,11,4,1,12,1,21,11,11,1,31,2,11,3,21,1,
%T A037916 111,1,5,11,11,11,22,1,11,11,31,1,111,1,21,21,11,1,41,2,12,11,21,1,13,
%U A037916 11,31,11,11,1,211,1,11,21,6,11,111,1,21,11,111,1,32,1,11,12,21,11,111
%N A037916 Concatenate exponents in prime factorization of n.
%C A037916 a(n)=1 for prime n; a(n)=11,111,1111,... if n=product of two, three, 
               four, ... distinct primes. Zak Seidov, Dec 15, 2006
%C A037916 The sequence of (nonzero) exponents in the prime factorization of a number 
               is called its prime signature. - M. F. Hasler (www.univ-ag.fr/~mhasler), 
               Apr 17 2008
%H A037916 Zak Seidov, <a href="b037916.txt">Table of n, a(n) for n = 1..2000.</
               a>
%H A037916 Wikipedia, <a href="http://en.wikipedia.org/wiki/Prime_signature">Prime 
               signature</a>.
%e A037916 12=2^2*3^1, so a(12)=21.
%o A037916 (PARI) A037916(n)=if( n>1, eval(concat(concat([""],factor(n)[,2]~)))) 
               - M. F. Hasler (www.univ-ag.fr/~mhasler), Apr 17 2008
%o A037916 (PARI) primesig(n)=sum(i=1,#n=vecsort(factor(n)[,2]),10^(#n-i)*n[i]) 
               \\ up to the order of digits, the same result up to 2^10. - M. F. 
               Hasler (www.univ-ag.fr/~mhasler), Apr 17 2008
%Y A037916 Sequence in context: A098290 A160110 A139393 this_sequence A143888 A016546 
               A141504
%Y A037916 Adjacent sequences: A037913 A037914 A037915 this_sequence A037917 A037918 
               A037919
%K A037916 nonn,easy
%O A037916 1,4
%A A037916 N. J. A. Sloane (njas(AT)research.att.com).
%E A037916 More terms from Erich Friedman (erich.friedman(AT)stetson.edu).