login
This site is supported by donations to The OEIS Foundation.
Logo

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

For each term a(n) in this sequence, A080153(n)=ithprime(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

Cf. A073640, A080153.

Sequence in context: A115248 A005123 A154732 * A069829 A022429 A020907

Adjacent sequences:  A080151 A080152 A080153 * A080155 A080156 A080157

KEYWORD

nonn,base

AUTHOR

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

EXTENSIONS

Edited by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Apr 30 2010

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 16 17:48 EST 2012. Contains 205939 sequences.