Search: id:A103839
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%I A103839
%S A103839 1,2,2,8,4,16,24,60,140,1328,2144,17536,23296,74216,191544,2119632,4094976,
%T A103839 24223424,45604056,241559918,675603568,8723487720,22850057800,285146572432
%N A103839 Number of permutations of (1,2,3,...,n) where each of the (n-1) adjacent 
               pairs of elements sums to a prime.
%F A103839 For n>1, A103839(n)=2*A051239(n).
%e A103839 For n = 5, we have the 4 permutations and the sums of adjacent elements:
%e A103839 1,4,3,2,5 (1+4=5, 4+3=7, 3+2=5, 2+5=7)
%e A103839 3,4,1,2,5 (3+4=7, 4+1=5, 1+2=3, 2+5=7)
%e A103839 5,2,1,4,3 (5+2=7, 2+1=3, 1+4=5, 4+3=7)
%e A103839 5,2,3,4,1 (5+2=7, 2+3=5, 3+4=7, 4+1=5)
%Y A103839 Sequence in context: A144847 A143625 A003612 this_sequence A135727 A075101 
               A075103
%Y A103839 Adjacent sequences: A103836 A103837 A103838 this_sequence A103840 A103841 
               A103842
%K A103839 nonn
%O A103839 1,2
%A A103839 N. J. A. Sloane (njas(AT)research.att.com), Mar 30 2005
%E A103839 More terms from Max Alekseyev, Jan 04 2008

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