Search: id:A145173
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%I A145173
%S A145173 0,1,2,1,2,4,2,1,4,9,1,2,14,2,3,9,2,9,24,1,25,1,7,8,2,52,14,13,42,7,22,
%T A145173 8,5,20,36,9,8,10,36,56,2,14,42,7,2,128,159,45,49,1,16,69,211,80,19,13,
%U A145173 3,12,25,21,106,32,39,26,21,23,5,22,66,43,45,139,350,38,26,145,19,142
%N A145173 Least a(n) such that p(n)#*(p(n)#-a(n))-1 is prime with p(i)#=i-th primorial.
%C A145173 As n increases the sum a(n) for i=1 to n tends to n*(n+1)/2.
%H A145173 Pierre CAMI, <a href="b145173.txt">Table of n, a(n) for n = 1..704</a>
%e A145173 2*(2-0-1=3 prime so a(1)=0 2*3*(2*3-1)-1=29 prime so a(2)=1 2*3*5*(2*3*5-2)-1=839 
               prime so a(3)=2
%o A145173 (PARI) { allocatemem(932245000); default(primelimit, 4294965247); n=0; 
               p=1; q=1; until (0, n=n+1; p=nextprime(p+1); q=q*p; for (a=0, 1000000000, 
               r=q*(q-a)-1; if (isprime(r), print(n, " ", a); write("b145173.txt", 
               n, " ", a); break;); ) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), 
               Jan 14 2009]
%Y A145173 Cf. A144946, A144947
%Y A145173 Sequence in context: A164281 A082693 A097082 this_sequence A082793 A114929 
               A152251
%Y A145173 Adjacent sequences: A145170 A145171 A145172 this_sequence A145174 A145175 
               A145176
%K A145173 nonn
%O A145173 1,3
%A A145173 Pierre CAMI (pierrecami(AT)tele2.fr), Oct 03 2008
%E A145173 Corrected by several correspondents, Jan 14 2009

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