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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. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 18 20:45 EDT 2021. Contains 345121 sequences. (Running on oeis4.)