Search: id:A137287
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%I A137287
%S A137287 2,21,221,2221,222221,2222221,222222221,2222222221,222222222221,
%T A137287 222222222222221,2222222222222221,2222222222222222221,
%U A137287 222222222222222222221,2222222222222222222221
%N A137287 a(n) = the number 2 written (p(n)-1)/2 times followed with digit 1; p(n) 
               n-th prime number; a(1)=2.
%C A137287 Sum of digits of a(n) = p(n).
%e A137287 p(7)=17; (17-1)/2= 8; a(7) = 222222221, 8*"2" concatenated with "1"
%Y A137287 Cf. A000040, A031974.
%Y A137287 Sequence in context: A131698 A163068 A109684 this_sequence A155872 A106412 
               A058476
%Y A137287 Adjacent sequences: A137284 A137285 A137286 this_sequence A137288 A137289 
               A137290
%K A137287 easy,nonn,base
%O A137287 1,1
%A A137287 Ctibor O. Zizka (ctibor.zizka(AT)seznam.cz), Apr 05 2008

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