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 A068698 Smallest primes in the reverse concatenation of n consecutive odd numbers. 0

%I #9 Dec 25 2022 12:39:20

%S 3,31,0,59575553,15131197,0,55535149474543,6361595755535149,0,

%T 1151131111091071051031019997,207205203201199197195193191189187,0,

%U 65636159575553514947454341,4543413937353331292725232119,0

%N Smallest primes in the reverse concatenation of n consecutive odd numbers.

%e a(5) = 15131197 is a prime and a concatenation of 15,13,11,9 and 7.

%p for n from 1 to 32 do d := 0:c := true: if((n mod 3)=0) then c := false:a := 0:end if: while(c=true) do a := 2*(n+d)-1:for j from 1 to n-1 do a := 2*(n+d-j)-1+10^( floor(evalf(log(2*(n+d-j)-1)/log(10))+0.0000000001 )+1)*a:end do: if(isprime(a))then c := false:end if:d := d+1:end do:b[n] := a:end do:seq(b[h],h=1..32);

%K base,hard,nonn

%O 1,1

%A _Amarnath Murthy_, Mar 04 2002

%E More terms from _Sascha Kurz_, Mar 27 2002

%E Definition clarified by _Harvey P. Dale_, Dec 25 2022

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Last modified August 11 23:45 EDT 2024. Contains 375082 sequences. (Running on oeis4.)