A121609 - OEIS

A121609

Composite numbers that can be written as concatenation of two primes in decimal representation.

22, 25, 27, 32, 33, 35, 52, 55, 57, 72, 75, 77, 112, 115, 117, 132, 133, 135, 172, 175, 177, 192, 195, 213, 217, 219, 231, 232, 235, 237, 243, 247, 253, 259, 261, 267, 273, 279, 289, 292, 295, 297, 312, 315, 319, 323, 329, 341, 343, 361, 371, 372, 375, 377

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

OFFSET

1,1

COMMENTS

Subsequence of A066737.

LINKS

Jean-Marc Falcoz, Table of n, a(n) for n = 1..11140

EXAMPLE

A002808(249) = 315 = 31*10+5 = A000040(11)*10+A000040(3),

therefore 315 is a term: a(44) = 315;

A002808(252) = 319 = 3*100+19 = A000040(2)*100+A000040(8),

therefore 319 is a term: a(45) = 319.