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%I #2 Mar 30 2012 17:26:30
%S 29231311,37231913,37311913,41231713,41291311,41291713,41292311,
%T 41292319,41311913,41312911,41312923,41372311,41372911,43191311,
%U 43231711,43311713,43311911,43371917,43412911,47231311,47231711
%N Primes n that are concatenation of four 2-digit primes in decreasing order.
%C n = 10^6*p+10^4*q+10^2*r+s, with primes p,q,r,s, 98>p>q>r>s>10.
%C There are 722 such primes from 29231311,37231913,37311913 to
%C 97897931,97897973,97898347.
%t pr2={97,89,83,79,73,71,67,61,59,53,47,43,41,37,31,29,23,19,17,13,11};
%t k=4;ssk=Subsets[pr2,{k}];Le=Binomial[21,k];
%t Reap[Do[If[PrimeQ[fd=FromDigits[Flatten[IntegerDigits/@ssk[[i]]]]],Sow[fd]],{i,Le}]][[2,1]]
%Y Cf. A168499, A168500, A168513.
%K base,fini,full,nonn
%O 1,1
%A _Zak Seidov_, Nov 28 2009
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