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A102499 Primes of the concatenated form 3nn3. 3
313133, 323233, 328283, 329293, 338383, 343433, 349493, 350503, 352523, 356563, 364643, 367673, 380803, 383833, 392923, 394943, 395953, 397973, 3100010003, 3100310033, 3102410243, 3102510253, 3102810283, 3103910393, 3104610463 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

313133 is prime and of the form 3nn3 for n=13.

3100010003 is prime and of the form 3nn3 for n=1000.

MATHEMATICA

mn[n_]:=Module[{idn=IntegerDigits[n]}, FromDigits[Join[{3}, idn, idn, {3}]]]; Select[mn/@Range[1100], PrimeQ]  (* Harvey P. Dale, Feb 04 2011 *)

CROSSREFS

Cf. A102896 for sequence of all numbers of form 3nn3. A102498 for the n values corresponding to the primes in this sequence.

Sequence in context: A250371 A210296 A214244 * A234121 A250152 A104826

Adjacent sequences:  A102496 A102497 A102498 * A102500 A102501 A102502

KEYWORD

easy,nonn,base

AUTHOR

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

STATUS

approved

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Last modified June 20 06:56 EDT 2021. Contains 345157 sequences. (Running on oeis4.)