A080156 Values of n corresponding to the terms in sequence A080155. For any k, the concatenation of the a(1) to a(k)-th primes is prime and each value of k is the smallest for which this is true.

1, 2, 5, 11, 15, 50, 54, 106, 148, 149, 156, 188, 200, 211, 248, 326, 359, 374, 417, 467, 699, 798, 891, 966, 1038, 1519, 1542, 1578, 1831, 1908, 1982, 2079, 2305, 2640, 2660, 2845, 3078, 3145, 3760, 3777, 3835, 4538, 4630, 4991, 5019, 5554, 5658, 5827

Offset: 1

Author

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

Keywords

• nonn
• base
• changed

Links

• T. D. Noe, Table of n, a(n) for n = 1..201

Crossrefs

Cf. A000720, A073640, A080152, A080153, A080154, A080155.

Programs

Maple

with(numtheory): pout := [2]: nout := [1]: for n from 2 to 5000 do: p := ithprime(n): d := parse(cat(seq(pout[i],i=1..nops(pout)),p)): if (isprime(d)) then pout := [op(pout),p]: nout := [op(nout),n]: fi: od: nout;

Formula

a(n) = primepi(A080155(n)) = A000720(A080155(n)).

Extensions

Edited by Charles R Greathouse IV, Apr 30 2010