Search: id:A109744
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%I A109744
%S A109744 1,2,3,4,5,12,42,48,9,90,22,96,299,154,60,288,918,1026,380,60,2184,616,
%T A109744 23,120,175,2964,135,980,319,1230,2015,2464,1056,272,2310,2448,111,
%U A109744 11628,2301,8800,7134,252,4730,3036,1665,3634,1551,2016,147,4950
%N A109744 Least multiple of n such that every partial concatenation followed by 
               a 7 is prime.
%e A109744 17,127,1237,12347,123457,... etc. are all prime.
%p A109744 Lcat := proc(L) local a,i; a := 0 ; for i from 1 to nops(L) do a := a*10^(max(1,
               ilog10(op(i,L))+1))+op(i,L) ; od: RETURN(a) ; end: A109744 := proc(nmax) 
               local a,k,n; a := [1] ; while nops(a) < nmax do n := nops(a)+1 ; 
               k := 1; while not isprime(Lcat([op(a),k*n,7]) ) do k := k+1 ; od 
               ; a := [op(a),k*n] ; od: RETURN(a) ; end: op(A109744(50)) ; - R. 
               J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 15 2007
%Y A109744 Cf. A110436, A110437.
%Y A109744 Sequence in context: A109849 A007662 A165303 this_sequence A065635 A101546 
               A026471
%Y A109744 Adjacent sequences: A109741 A109742 A109743 this_sequence A109745 A109746 
               A109747
%K A109744 base,nonn
%O A109744 1,2
%A A109744 Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 03 2005
%E A109744 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 15 2007

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