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

3, 31, 0, 59575553, 15131197, 0, 55535149474543, 6361595755535149, 0, 1151131111091071051031019997, 207205203201199197195193191189187, 0, 65636159575553514947454341, 4543413937353331292725232119, 0

Offset

1,1

Links

Table of n, a(n) for n=1..15.

Example

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

Maple

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);

Crossrefs

Sequence in context: A155731 A145385 A059232 * A053300 A322777 A089281

Adjacent sequences: A068695 A068696 A068697 * A068699 A068700 A068701

Keyword

base,hard,nonn

Author

Amarnath Murthy, Mar 04 2002

Extensions

More terms from Sascha Kurz, Mar 27 2002

Definition clarified by Harvey P. Dale, Dec 25 2022

Status

approved