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Let a (resp. b,c,d) be number of primes in the range {2..p} that end in 1 (resp. 3,7,9); sequence gives p such that a=d and b=c.
1

%I #3 Sep 21 2005 03:00:00

%S 2,7,19,37,139,151,163,173,181,199,229,397,409,421,491,557,577,593,

%T 601,613,659,809,839,857,881,887,1439,1459,1657,1667,1889,2029,3023,

%U 3863,4283,5261,5297,5437,5479,7853,7873,7901,8263,8291,8297,8353,8521,8597

%N Let a (resp. b,c,d) be number of primes in the range {2..p} that end in 1 (resp. 3,7,9); sequence gives p such that a=d and b=c.

%e E.g. n=19 {2,3,5,7,11,13,17,19}->{2,3,5,7,1,3,7,9}, a=1, b=2, c=2, d=1, b=c and a=d, therefore accept 19.

%Y Cf. A038563.

%K easy,nonn

%O 2,1

%A Author's name lost.