A080154 - OEIS

%I #10 May 26 2018 08:44:16

%S 1,2,5,9,11,13,17,22,25,28,30,36,38,41,45,48,49,53,55,58,68,76,84,85,

%T 91,94,101,114,137,139,147,153,154,156,163,165,180,189,195,200,210,

%U 211,223,235,237,241,246,247,249,253,256,272,274,286,289,293,296,306,321,323

%N Values of n corresponding to the terms in sequence A080153.

%F For each term a(n) in this sequence, A080153(n) = prime(a(n)).

%e E.g. the first three terms are 1, 2 and 5 because the concatenation of the first, 2nd and 11th primes is 2311 and this is prime. Also, the 5th prime is the first one after 3 for which this concatenation is prime.

%p with(numtheory): pout := [2,3]: nout := [1,2]: for n from 3 to 600 do: p := ithprime(n): d := parse(cat(pout[nops(pout)-1],pout[nops(pout)],p)): if (isprime(d)) then pout := [op(pout),p]: nout := [op(nout),n]: fi: od: nout;

%Y Cf. A073640, A080153.

%K nonn,base

%O 1,2

%A Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 31 2003

%E Edited by _Charles R Greathouse IV_, Apr 30 2010