%I A007603 M0480
%S A007603 1,2,3,4,5,6,7,8,9,10,12,18,20,21,23,24,27,30,36,40,42,45,48,50,54,60,
%T A007603 63,70,72,80,81,84,90,100,102,104,108,110,111,112,113,114,115,116,117,
%U A007603 120,122,126,130,131,132,133,134,135,136,140,144,150,151,152,153,154,156,
               160,162,170,171,172,173,174,178,180,182
%N A007603 Power-sum numbers: let n = a_1 a_2 ... a_k be a k-digit number; n is 
               a power-sum number if there are exponents e_1 ... e_m such that n 
               = Sum_{i=1..m} Sum_{j=1..k} a_j^e_i.
%D A007603 M. Keith, Power-sum numbers, J. Rec. Math., 18 (No. 4, 1986), 275-278.
%D A007603 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%e A007603 21 = (2+1)+(2^3+1^3)+(2^3+1^3), with e_1, e_2, e_3 = 1, 3, 3.
%Y A007603 Sequence in context: A059765 A143289 A064807 this_sequence A005349 A085135 
               A085133
%Y A007603 Adjacent sequences: A007600 A007601 A007602 this_sequence A007604 A007605 
               A007606
%K A007603 nonn,easy,nice
%O A007603 1,2
%A A007603 N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com), 
               Mira Bernstein (mira(AT)math.berkeley.edu)
%E A007603 Corrected and extended by Naohiro Nomoto (6284968128(AT)geocities.co.jp), 
               Mar 11 2001