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A080154
Values of n corresponding to the terms in sequence A080153.
1
1, 2, 5, 9, 11, 13, 17, 22, 25, 28, 30, 36, 38, 41, 45, 48, 49, 53, 55, 58, 68, 76, 84, 85, 91, 94, 101, 114, 137, 139, 147, 153, 154, 156, 163, 165, 180, 189, 195, 200, 210, 211, 223, 235, 237, 241, 246, 247, 249, 253, 256, 272, 274, 286, 289, 293, 296, 306, 321, 323
OFFSET
1,2
FORMULA
For each term a(n) in this sequence, A080153(n) = prime(a(n)).
EXAMPLE
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.
MAPLE
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;
CROSSREFS
Sequence in context: A284875 A154732 A242936 * A069829 A022429 A020907
KEYWORD
nonn,base
AUTHOR
Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 31 2003
EXTENSIONS
Edited by Charles R Greathouse IV, Apr 30 2010
STATUS
approved