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A106550 a(n) = n-th semiprime + (concatenation of its two prime factors, smallest factor first). 4
26, 29, 42, 35, 41, 50, 58, 233, 80, 239, 344, 251, 92, 257, 352, 269, 126, 368, 566, 376, 287, 293, 578, 392, 311, 788, 323, 602, 329, 416, 804, 424, 341, 614, 359, 448, 638, 377, 836, 1232, 383, 464, 472, 852, 401, 488, 413, 1256, 674, 419, 686, 437, 512, 884 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = A001358(n) + A106554(n). - Reinhard Zumkeller, May 19 2005
EXAMPLE
First semiprime is 4; 4 is 2*2; 26=4+22.
Second semiprime is 6; 6 is 2*3; 29=6+23.
Third semiprime is 9; 9 is 3*3; 41=9+33.
Fourth semiprime is 10; 10 is 2*5; 35=10+25.
MATHEMATICA
R=165; SP=Select[Range[R], PrimeOmega[#]==2&]; FromDigits@ Flatten[IntegerDigits@ Table[#1, {#2}] & @@@ FactorInteger@ #] & /@ SP +SP (* James C. McMahon, Feb 18 2024 *)
CROSSREFS
Sequence in context: A256619 A055109 A106552 * A304949 A316617 A303815
KEYWORD
base,easy,nonn
AUTHOR
Eric Angelini, May 09 2005
EXTENSIONS
More terms from Reinhard Zumkeller, May 19 2005
Typo corrected by James C. McMahon, Feb 06 2024
STATUS
approved

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Last modified March 28 17:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)