A080152 - OEIS

A080152

Values of n corresponding to the primes given in A073640. The concatenation of the a(n) and a(n+1)th primes for any n is also prime.

1, 2, 4, 8, 11, 12, 18, 21, 31, 34, 46, 47, 50, 61, 78, 84, 85, 90, 99, 100, 101, 106, 110, 111, 114, 131, 133, 138, 141, 157, 159, 167, 169, 172, 175, 183, 197, 198, 211, 229, 231, 232, 233, 235, 260, 261, 269, 276, 285, 289, 295, 306, 322, 337, 339, 340, 347

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..57.

FORMULA

A073640(n) = prime(a(n)), with a(n) the n-th term in this sequence.

EXAMPLE

E.g. For n=5: a(5)=11, a(6)=12 and the concatenation of 11th and 12th primes is 3137, which is also prime. The 5th and 6th terms in A073640 are 31 and 37.

MAPLE

nout := [1]: for n from 2 to 1000 do: p := ithprime(n): d := parse(cat(pout[nops(pout)], p)): if (isprime(d)) then nout := [op(nout), n]: fi: od:

CROSSREFS

Cf. A073640.

Sequence in context: A174781 A028846 A274924 * A136994 A137288 A247524

Adjacent sequences: A080149 A080150 A080151 * A080153 A080154 A080155

KEYWORD

nonn,base

AUTHOR

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

EXTENSIONS

Edited by Charles R Greathouse IV, Apr 26 2010

STATUS

approved