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 A254718 a(n) is the least semiprime having a(n-1) as a substring, a(1)=4. 1
 4, 14, 141, 1141, 11141, 111413, 1111413, 11114137, 111114137, 1111141373, 11111141373, 111111413737, 1111114137373, 11111141373734, 1111114137373402, 11111141373734023, 111111413737340234, 11111114137373402349, 111111114137373402349, 1111111141373734023499 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Jon E. Schoenfield, Table of n, a(n) for n = 1..71 Jon E. Schoenfield, Terms and factors for n = 1..71 Jon E. Schoenfield, Terms and factors for n = 1..71 and tentative additional terms through n=84 EXAMPLE 4=2*2, 14=2*7, 141=3*47, 1141=7*163, 11141=13*857, 111413=43*2591, 1111413=3*370471, 11114137=47*236471, 111114137=31*3584327, 1111141373=1051*1057223. CROSSREFS Cf. A001358, A030456. Sequence in context: A006824 A333730 A344201 * A162077 A247526 A111266 Adjacent sequences: A254715 A254716 A254717 * A254719 A254720 A254721 KEYWORD nonn,base AUTHOR Zak Seidov, Feb 06 2015 EXTENSIONS a(11)-a(20) from Jon E. Schoenfield, Feb 19 2015 STATUS approved

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Last modified April 16 19:48 EDT 2024. Contains 371754 sequences. (Running on oeis4.)