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A083190 a(1) = 1; for n>1 a(n) is smallest prime not occurring earlier such that the concatenation of a(n), a(n+1), ..., a(2n-1) is a composite number. 1
1, 2, 5, 3, 7, 11, 13, 17, 23, 19, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..60.

EXAMPLE

1, 25, 537, 371113, 711131723 are composite numbers. Note that 711131719 is a prime hence a(9) = 23 and not 19.

CROSSREFS

Cf. A083191.

Sequence in context: A289108 A246364 A352774 * A171026 A064359 A309006

Adjacent sequences: A083187 A083188 A083189 * A083191 A083192 A083193

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Apr 27 2003

EXTENSIONS

Extended by Ray Chandler, Jan 04 2009

STATUS

approved

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Last modified November 28 22:51 EST 2022. Contains 358421 sequences. (Running on oeis4.)